Single Line of Descent

A curious phenomenon where there's only one true descendant of some legendary hero/villain or chosen one. Usually it's only that one person who can save the day or bring about The End of the World as We Know It. Because Destiny Says So, of course. And often it has to be the male line, or whichever keeps the last name (and even that can be problematic, as family names evolve over time, or even change completely). The fact that there's multiple branching into different last names doesn't count genetically for some bizarre reason.

This is curious in itself. Most family trees branch quite a bit due to multiple children having multiple children (and families of important lineage in particular tend to make a point of having a "spare" heir around to avert any potential Succession Crisis). In fact, if you look far enough into the past, you reach a point where every human being alive then is either the ancestor of everybody or nobody who is currently alive. Here apparently only one child was born per generation. In older legends, it was explicitly stated that only the firstborn "counts", but the socio-economic systems that fostered that kind of thinking withered away, leaving only this trope.

Similarly, the sole true descendant is generally treated as essentially equivalent to their ancestor, having the same powers, personality, ethnicity, and so on. Never mind that, if the legendary hero lived twenty generations ago, he had roughly a million contemporaries who are just as closely related to the modern-day version as he (assuming no inbreeding, every person has two parents, four grandparents, eight great-grandparents, sixteen great-great-grandparents, 32 great-great-great-grandparents...).

Note that, in the present generation, if there is another sibling, they tend to be recruited by the Big Bad as the Evil Counterpart.

Occasionally it will be explained away that the Big Bad found and eliminated the rest, and the Supporting Leader happened to get to the last one in time.

Possibly related to the Identical Grandson. Only one in a generation can take the "legacy." Explanations that a family produces Single Sex Offspring may be given as an attempt to justify this trope, especially if they are all male.

The last offspring of a Single Line of Descent is by definition the Last of His Kind. Also see Royal Inbreeding (fiction often ignores the biological consequences of inbreeding).

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Examples:

Anime and Manga

• In Blue Seed, there is only one (well, two) people left of a bloodline whose lifeforce can destroy the Aragami.
• Raideen: Akira Hibiki is a descendant of the ancient people of Mu and he must help Raideen save the Earth. With Akira, the line of descent doesn't extend very far. His mother is the queen of Mu.
• Naruto:
  • Averted with the Sage of the Six Paths, who spawned the Uchiha, Senju, and Uzumaki clans. In the case of the Uzumaki and Uchiha clans, Naruto and Sasuke being the only descendants is justified because they are also the only survivors of the clans being annihilated, though it turns out with the Uzumaki that Karin is another descendant to survive through the end of the original series, though her exact relationship to Naruto isn't clarified.
  • In addition, the Hyuga clan is split between a small head family and several branch families; if the Hyuga head has multiple children, then only one inherits a position in the head house, with the rest relegated to forming their own branch houses. The Moon Otsutsuki also had a similar arrangement; perhaps not coincidentally, both them and the Hyuga are descended from the Sage's twin brother.
• The Nakatsukasas in Soul Eater. The eldest child is expected to inherit the Morph Weapon ability, and Masamune took issue with the fact he did not. Odd, in that the Demon Weapons are the result of experimentation and that Tsubaki's family is quite clearly not the only example. In fact, the others have branched out into more modern and outlandish interpretations of the word 'weapon'.
• Enforced in the Nasuverse, where magi generally only pass on magic to a single heir because doing otherwise would divide the family's source of magic between them. Defied in the case of Tohsaka Tokiomi, who upon siring two talented daughters, made Rin his heir and gave Sakura to be the heir to the heir-less Matou house. The only problem is the Matou family treated Sakura horribly.
• The Raregroove family in Rave Master doesn't boast any cases of multiple children. Understandably, since they are a bloodline of Cosmic Playthings who apparently tend to lose anyone they cherish in very brutal ways. Because of this, Lucia ends up being the sole descendant of Acelia, the last human not to be created by Star Memory.
• JoJo's Bizarre Adventure is a Generational Saga following the descendants of Jonathan Joestar. The first five generations (and three protagonists) are only children. While several of the Joestars only lived long enough to have one child, the second protagonist (Jonathan's grandson Joseph) lived at least into his 80s yet he and his wife still only had a single daughter. Things get more complicated from then on, as the next two protagonists are a newly-found illegitimate child of Joseph and a child of Dio possessing Jonathan's body. Even by the fourth generation, the family name would change, but retain a "Jo" syllable to continue being JoJo.
• Subverted in Senyuu.. When the king calls for descendants of an ancient hero who lived a thousand years ago, he discovers that a guy who lived a thousand years ago can have a lot of descendants. Then averted entirely when the hero was alive all along, and never had any descendants.
• Consciously averted in Cool-Kyou Shinsha's work Fukumaden, where the hero is given a massive harem to ensure that his bloodline survives until the demon lord's eventual resurrection.
• Used in Attack on Titan, doubled with Last of His Kind and There Is Another. There's Historia, who becomes queen of the walls after learning that she's the last remaining member of the Reiss family and that the current royal family are puppets. Then you have Zeke Yeager, the last living Fritz, at least outside the walls. He's a direct descendant of Ymir Fritz, the supposed creator of the Titans, through his mother Dina. Of course, the two families are one in the same: the Reiss family are the side of the Fritz family that are within the walls, and the Fritz are the side of the family that stayed on the continent until they were mostly wiped out.
  • Also applies to noble families, such as the Tybur family, who are the true rulers of the Kingdom of Marley and the family that possesses the Warhammer Titan.
• Undefeated Bahamut Chronicle has a justified example in the Arcadia family, whose only survivors are Lux, Airi, and Fugil (all children from the same father) because Fugil killed everyone else. The light novels later reveal that this trope is subverted altogether, as the modern Arcadia family is a branch of the main line. The branch family led a rebellion against and massacred most of the main family. The survivors went into stasis to hide but were found by the branch family who then attempted to finish the job. Fugil (who turns out to not be part of the family at all) stopped them, leaving only three sisters (Listelka, Aeril, and Hayes) as the last survivors of the main family.
• Averted in Yona of the Dawn.
  • Everyone in the dragon villages is descended from one of the Four Dragons, but a maximum of two people can share the dragon's power at the same time; there's a limited pool of power, so when a new dragon is born, the old one becomes weaker and dies young. The current White Dragon happened to be the son of the previous White Dragon, but that's not necessarily the rule. The village of the Blue Dragon treats the power as a curse that can strike any of their children even if the previous Dragon did not reproduce, and the previous Green Dragon didn't anticipate the current Green Dragon's birth, implying that he was not the father. And the Yellow Dragon never passed on his powers, because he's immortal.
  • Late into the series, we also learn more about the Crimson Dragon King's line of descent: he had five children, and although his descendants eventually lost the throne, at least two different lineages are still extant.
• Sailor Moon: In the manga it's stated that Moon royals could only have one heir, in dismissing the idea that Chibi Chibi could be a second child of Usagi and Mamoru.

Comic Books

• 100 Bullets: The thirteen families of the Trust have been in a position of power over America since it was first settled. Several families in the present day have multiple children, indicating they have never been restricted to just having a single child. Nonetheless, several families (Vasco, D'Arcy, Dietrich, and Vermeer) have no heirs who can succeed the family heads should they die (although it is possible that only adult children of current leaders can be heirs).
• Both used and averted with the immortal Vandal Savage, who has multiple descendants apparently including Arsenal whom he harvests for organs, and a person he specifically identifies from among them as his daughter Scandal, leader of the Secret Six. According to Scandal, her legitimacy is down to the fact Vandal married her mother.
• In Batman, Bruce Wayne is the only Wayne heir as he is an only child of an only child father. His dad had a brother prior to the 80s named Philip but now Uncle Philip is his mom’s brother. Somewhat subverted in the third generation as he only has a biological child, Damian, but he has four other adopted children (three boys, one girl). Young Damian will be the first Wayne in three generations to have to split the inheritance.
• Star Wars: Legacy seems to hint that this happened. It's been a hundred fifty years, and the only Skywalkers alive are Cade and his immediate relatives. It's hinted that the Organa Solo line got absorbed into the Antilles Fel line, whose descendant is the Emperor. The second volume starred Ania Solo, the previously unknown last member of the Solo-Djo line (and the only person known to still use the Solo surname), but the book was cancelled before more details about the family could be established.
• In the Pre-Crisis Legion of Super-Heroes comics, Laurel Kent is Superman and Lois Lane's only known descendant in the 30th century (before being retconned out).
• Disney Ducks Comic Universe: In The Life and Times of Scrooge McDuck by Don Rosa, Scrooge McDuck is often lauded as the last of the once great Clan McDuck, whose lineage contains knights, merchants, magnates, Templars, and all manner of greatness. This despite the fact that he is only the last MALE member of the Clan, and his two sisters apparently not counting, one of whom had children and grandchildren of her own, these of course being his nephew Donald Duck and his nephews.
  • However, various stories by different writers seems to contradict this fact, as many male living cousins of Scrooge McDuck who also holds the last name McDuck were introduced throughout the years.
• The Metabarons: Very much the case with the Castakas. A couple of Metabarons actually end up having more than one child, but no collateral family lines are ever formed. Othon's first son Bari is accidentally killed by him when still a teenager and Steelhead's son (Aghora's twin) dies at birth.
• X-Men: Colossus Bloodline: Piotr's ancestor, Grigori Rasputin, had many descendants, but Mr. Sinister has been hunting them down and killing them so Grigori can reincarnate in the last one left.

Comic Strips

• In The Phantom, natives and pirates are led to believe that the masked crime fighter is the same man living for hundreds of years. He is, in fact, the son of the last guy. Multiple Phantoms have had more than one child, but once an inheritor is chosen, his siblings usually disappear from history and are never mentioned again. This is most notable with the 13th Phantom, who was the youngest of 4 sons, none of whom are ever seen or mentioned again outside his origin story. There was also the twin sister of the 17th Phantom who occasionally filled in for him, but is not known to have had any children of her own.

Fan Fiction

• Cheating Death: Those That Lived: The Flawless Estate contains District 1's 12 richest and most powerful families, but seven of those families only have a single heir or heiress and most of those lone heirs or heiresses kill each other while training for the games or successfully become tributes but then die (one wins and a few who are of the right age and survive training don't become tributes for one reason or another). Houses Goldclaw, Fragrance, Platinum, Court, and Royalty have multiple children, but at least two of them still go extinct. Both Royalty kids compete in the same games and neither comes home, while the older Court siblings commit Brother–Sister Incest to turn out a new heiress, who becomes a victor but then is so unstable that Snow has her killed.
• Dangerverse: All four of the Founders' bloodlines seem to have been whittled down to a single family: Remus Lupin is the last living descendant of Godric Gryffindor, Frank and Neville Longbottom are the last remaining Heirs of Hufflepuff, etc.
• In A Great And Powerful Legacy, Trixie is revealed to be the sole living descendant of Starswirl The Bearded. However, it's established that the line tended toward having only one or two children each generation, and with only one continuing the line.
• Hellsister Trilogy: In the 30th century, there is only one surviving member of Clark Kent's bloodline, Laurel Kent.
• Cosmo Hender from Alien Exodus is the sole descendant of Dale Hender.
• Lampooned in Superman of 2499: The Great Confrontation. In the 25th century, the descendants of the first Superman and Supergirl are a very large family who have spent five centuries enforcing the masquerade that every Superman has one single descendant who becomes the next Man of Steel. George Kent scoffs at the notion that Earth people are stupid enough to believe that, but his nephew Alan argues the sham must be maintained for their peace of mind.
  George: Alan... Alan... Just how stupid do you think the average man is, boy?
  Alan: (sighing) I don't know, Uncle George. You tell *me*. How stupid *do* I think the average man is?
  George: Pretty damn stupid, Alan. For over five hundred years there's been a Superman. Since the Prime Superman of the Twentieth. Everyone knows that. Don't you imagine that the general populace might— just might, mind you!—have figured out that, by the simplest laws of genetics and mathematics, there *has* to be more than one of us?
  Alan: Of course, they know, Uncle George. Most of them. When they think about it. Which isn't often. Uncle George, don't *do* this. Please. Listen to me. As long as we don't rub their faces in it ... as long they see only one of us, a hero, they aren't threatened.
• In Spectrum, after a thousand years and a purge by King Sombra, Cadance is apparently the last living direct descendant of Princess Luna. However, Celestia notes the implausibility of it all, and wonders how Cadance really can be Luna's last scion. It's quite strongly hinted that Radiant Hope is her mother, significantly narrowing the family down.
• Discussed during the Chamber of Secrets arc of The Odds Were Never In My Favour. When discussing who could be the Heirs of the Founders, it is mentioned that the Ravenclaw line is definitely extinct (Rowena's only child died childless), the Slytherin line is believed extinct (after the last Gaunt died in Azkaban), and that Gryffindor was a notorious womanizer and that it would probably be easier to name the people in magical Britain who aren't descended from him somehow.
• Queens of Mewni: Because of Queen Venus's addiction to bloomoon tea, which unknown to her had a contraceptive effect, her descendants all had trouble conceiving and would only end up conceiving one heir except Eclipsa, who managed two, and Luna, who would miscarry eight previous pregnancies before finally giving birth to Heaven until Queen Vesper would find a cure and produce multiple heirs to the Butterfly throne for the first time in 300 years.

Film — Live-Action

• A character in Dogma is the only member of Jesus's brother's bloodline (through a sibling of the "ancestor" instead of the "ancestor" himself).
• In Underworld (2003). The Lycans are searching for a human descendant of the progenitor of both werewolves and vampires, but they need one with a specific gene and a wall filled with crossed over photographs tell us that there has been a lot of failures before the events of the movie. But that's because all they have to go on to find that one descendant is his last name, Corvin, which isn't exactly rare or unique. Depending on how long they've been looking for this guy, and killing the ones who don't meet their specifications, the Lycans may be the reason there's only a single line of descent.
  • It's not clear if they look anywhere else besides Hungary. The novelization mentions that Michael's grandfather emigrated from Hungary to the US and Anglicized his name from Corvinus to Corvin. Michael only decided to go back to the Old Country after his wife died. It may have been sheer luck that the Lycans have found the right person.
  • It's never actually said that Michael is the only descendant, the Lycan's are specifically looking for a descendant who is a "pure enough source of the bloodline", ie. he's just more closely related to a specific common ancestor than the other people they've tested so far. He's not even necessarily special in any way, there could be plenty of others as close or even more closely related, he just happened to be the first one they found who was suitable for the experiment.
• The Shadow, the Big Bad is the last descendant of Genghis Khan. And now compare this to what is written in the Real Life section.
• Explained in The Covenant that only the firstborn males in each generation receive powers. There may well be many descendants of the original (male) witches of Salem, but only five males with the Power per generation (there are five families).
• In the movie of The Da Vinci Code, there is only one surviving member of Jesus's bloodline. (In the book, though, the corresponding character has a sibling, and it's stated that they aren't the only line of descent, just the most reinforced and "qualified". That apparently wasn't dramatic enough for the movie, though.) This can be handwaved by the Opus Dei hunting down and eliminating all the other descendants.
• Halloweentown: The Cromwell family of witches has been around since the beginning of time, and yet Aggie says that if Gwen keeps her children from becoming witches, it will be the end of their magical bloodline.
• Van Helsing: Nine generations of the Valerious family have fought Dracula. Anna Valerious is the only one left to bear the family name and carry on their crusade after her brother is turned into a werewolf.

Literature

• Averted in Mikhail Akhmanov's Arrivals from the Dark and Trevelyan's Mission with the bloodline of Paul Richard Corcoran. Corcoran himself has two daughters, and each of his descendants has at least two children. However, the farther "down" the line we go, the less his Faata genes manifest themselves. The most common form is unnatural longevity coupled with sterility until 40. A few individuals do get his Psychic Powers as well. Sergey Valdez, Corcoran's great-grandson is notable for having these powers and passing them to both of his children. The last book of the Trevelyan's Mission series reveals that the protagonist Ivar Trevelyan is a 1000-year removed descendant of Corcoran with latent abilities.
• The Belgariad:
  • The book series featured the bloodline of the Rivan king, which usually only had one child per generation for centuries. This is justified due to prophecy keeping the family small so as to be easier to hide from numerous enemies. Seeing as almost the entire family was killed when they were secure on a small island surrounded by guards, this may be a good idea. Interesting in that the subject matter of one of the prequel books covers how the family was hidden/protected.
  • In Polgara the Sorceress, Cherek wives of the descendants of the Rivan kings always had lots of babies. Garion likely has bunches of n-th cousins running around, although he's never met them - and given how long ago his ancestors were in Cherek, the actual connection is probably non-existent. He does meet a first cousin at one point who becomes a recurring secondary character, with whom he is Like Brother and Sister, and there's technically a whole Algar clan of relatives as a result, but the Algar side is explicitly the maternal, non-royal, side of his family. Technically noble, but non-royal. It's been made clear to Polgara, during their time hiding among the Alorns, that the number of kids doesn't matter; the first-born son is the next hidden heir -"with or without benefit of clergy".
• Averted in A Brother's Price, or played straight, depending on how you look at it: all sisters in a family usually marry one husband. All their children are considered children to all of the mothers. Which means that all the princesses have an equal claim to the throne—and will rule together. However, it is possible to split the family, with the younger sisters marrying a different husband. This was once done by the royal family and resulted in a civil war over the question of whose group of sisters' offspring were to inherit the throne. The protagonist, Jerin, is descended from a prince who might have been killed in said civil war, and has no claim to the throne—but it does look nice on his birth certificate, and makes him an eligible candidate for marrying the princesses... as well as a potential kidnapping victim, as marrying him could give a woman some claim to the throne if all other potential heirs were dead. Very unlikely with ten living heirs, but the villains intend to find a way...
• Buffyverse: In The Gatekeeper Trilogy, there has only ever been one heir to the Regnier family Gate Guardian job at a time since Richard became the Gatekeeper, making Jacques the only Regneir left to continue the line. Although Richard's wife was murdered soon after the birth of their son and Jean-Marc's wife went insane and committed suicide, it can seem odd that Henri and Antoinette only ever had one child.
• In Codex Alera, the House of Gaius is mused at one point to have never been particularly prolific, with one politically astute character noting that current First Lord Gaius Sextus probably wouldn't have minded that much if his son, the late Gaius Septimus, had had a bastard child or two (given that Sextus is "a manipulative old serpent", probably because they could be politically useful and create cadet lines) if he'd gone on to make a suitable political marriage. However, Word of God explains that the counting system for monarchs restarts every time a branch of the family dies out, implying that at least some previous members have managed more than one child.
• Deltora Quest establishes that by tradition, the ruler of Deltora has only one child, meaning during the time of Deltora Shadowlands, Adin (the first king) has only one heir. If that heir dies childless, the power of the Belt will be lost forever. This was enforced by the succession of Evil Chancellors secretly working for the Shadow Lord, in order to set up the loss of power of the Belt. It's eventually subverted, as Adin himself had multiple children, who also did. By the present day, there are enough potential heirs if you know where to look for them that the Belt of Deltora can easily confirm as an heir to make wiping out the royal line an impractical strategy. When a young woman from the city of Tora named Marilen takes up residence in the palace, Jasmine assumes that Lief is going to make a political marriage, but actually she's the next in line and is there to wear the Belt while Lief is on the journey to the Shadowlands.
• In A Discovery of Witches, Diana is the last Bishop and possibly the last Proctor, as we never hear about Stephen having any other family.
• Carrot Ironfounderson is apparently the last living direct descendant of the Discworld's last Kings of Ankh. This has been supported by evidence uncovered by Edward d'Eath in Men at Arms, and by Dragon King of Arms' inability to find a better alternate successor than Nobby Nobbs in Feet of Clay. By the latter book, it's an Open Secret, but Carrot goes out of his way to destroy the evidence whenever he can and obliquely explains to Vetinari that he doesn't want the throne, preferring to be a Watchman because then people would obey him because it's the right thing to do, rather than because he's Carrot, and he'd only take it if there was no alternative. In Carrot's case, the lack of other heirs is at least implied to have been engineered, as he was the Sole Survivor of an attack on a caravan in which the long-lost royal sword had been carefully hidden.
  • Interestingly, the first time the royal line of Ankh-Morpork was a major plot point, the ringleader of the cult that set a dragon loose on the city actually lampshaded the trope as nonsense: Even if the line had survived at all, by now it'd be so watered down that there could be thousands of claimants. Their prospective king was a useful idiot who'd sign on the dotted line where he was told to and not make waves. Unfortunately for him, this plan was derailed by a quite literal Dragon with an Agenda...
  • Technically also true of Carrot's girlfriend Angua, who (post-The Fifth Elephant) is the sole surviving potential heir to her father's Barony in Uberwald. Played with in that she does have a living brother, Andrei, but as a "yennork" - a werewolf permanently locked into a single form - he was driven out of the family years ago to make a living as a sheepdog.
• Dortmunder: In Bad News, to fool a DNA test, Dortmund needs to steal the hair of a descendant of a man who died seventy years ago. They find a total of one adult descendant, who (along with her three daughters) is the live-in caretaker of a tightly-guarded art museum. Earlier generations of the family had more than one kid, but her aunt died in a car accident as a teenager, and her great-aunts were a nun and a lesbian, respectively, so none of them produced any additional branches of heirs.
• The Fall of the House of Usher is a classic example, as the once-noble Usher family is described as having produced no side-branches and declined to the point that only two frail siblings remain. The twist is that it happened because of Brother–Sister Incest, and there's a "taint" on the Usher house that could just be the typical health/physical issues that crop up after generations of Royal Inbreeding.
• The Hardy Boys: In Night of the Werewolf, legend has it that every seventh generation, a member of the Taber family turns into a werewolf. The Hardys speculate that there must be lots of Tabers besides their client's son who could be the victim of the curse (assuming it's even true). Their client regretfully informs them that the other branches of the family were almost entirely wiped out in World War II.
• In Harry Potter, Voldemort is the last descendant of Salazar Slytherin, one of the four founders of Hogwarts. It is Justified by explaining that Slytherin's descendants became so obsessed with keeping the line "pure" that they repeatedly married within the family.
• Herland: Herland's women are all descended from one woman who (after their men died out) then had inexplicably given birth to a child by parthenogenesis. This mutation passed down from her daughters.
• M.P. Shiel's "House of Sounds" has a family that once numbered in the millions dwindling down to three. A partial subversion, in that the declining bloodline is traced through both sexes, with the Last of His Kind descendant being born to parents deriving from two distant branches of the family.
• In the Hollow Kingdom Trilogy, both the Elf and Goblin Kings only ever have one son apiece. None of those messy succession debates here, no sirree!
• Dune:
  • In Legends of Dune, Camie Boro claims to be the only descendant of the last emperor of the Old Imperium. Given that the Old Imperium fell over 1000 years before, this is not very likely.
  • Averted with Vorian Atreides. During the Jihad days, he had so many lovers on so many planets, that he frankly lost track of all his descendants. This means that House Atreides in the main series (taking place over ten thousand years later) is far from the only source of Atreides blood. In fact, the founder of the Bene Gesserit school is actually Vorian's granddaughter, but that line does not last beyond 2 more generations.
  • For that matter, the Atreides themselves claim to be descended from King Agamemnon of Ancient Greece. Good luck proving that more than ten thousand years on.
• Not so in J. R. R. Tolkien's The Lord of the Rings, where multiple lines and descendants exist. An example are the kingdoms of Arnor and Gondor, respectively founded by Elendil and his sons, who are descended from a sideline branch of the Númenórean royal family: in both cases there are various people (both properly royal and more mundane ones) appearing and mentioned as descending from the same ancestor as the "main descendant(s)" of that line. Gondor even eventually endured a civil war over the question of inheritance, had problems with multiple potential claimants, and eventually no viable successor could be found who would have pleased everyone, resulting in the Stewards taking over. When the Gondorians first had trouble finding a royal successor, the Arnorian line and kingdom was still fully intact, and the Arnorian king tried to take over (on account of both dynasties being descended from Elendil and being married to the last Gondorian king's daughter) but was rejected. His descendant Aragorn would later succeed where he had failed. By which point, however, Aragorn basically was the last direct descendant of Elendil, thus re-invoking the trope. However, his claim was still tenuous enough that he only got the job because he had just saved the city and fulfilled a prophesy.
• In The Lost Prince, this is apparently the case for the Lost Prince's secret line of descendants; at the time of the novel, there are two living descendants, father and son, who are apparently descended in an unbroken line and both bear a striking resemblance to the surviving portrait of their revered ancestor.
• Played with in the Mithgar series with the "Lastborn Firstborns". A pair of mortal lovers become involved in a quest, but after a point, they're going to have to wait centuries to carry out the next step. They get married and pass their lore and quest items down the generations, hers to her firstborn daughter and then her firstborn daughter and so on, his to his firstborn son and so on. When the destined time finally rolls around, we end up with two characters who each look very similar to the ancestor whose lines of descent they've been following, but are no longer closely related. So they meet up, fall in love, and continue the quest, just like their ancestors. Then one of them dies, breaking the line of firstborns.
• Old Kingdom: At the time of Sabriel, there is only one remaining member of the Abhorsen bloodline (the titular character) and one remaining living royal (Touchstone) which is a big problem as both bloodlines are needed to respectively keep the dead from coming back to life and maintain the magical wards that protect the kingdom. Both cases are justified: it's implied that the chaos of the Interregnum, which led to the Old Kingdom's population declining substantially, reduced the numbers of the Abhorsen bloodline substantially as well; and all the royals were killed specifically to break the wards as royal blood is needed to do so, and said survivor is actually a bastard child of the Queen who was magically sealed away to protect them. The prequel Clariel shows that in the past this wasn't the case and that the royals, Abhorsens and Clayr once intermarried frequently, with the title character possessing the first two in her bloodline. The Clayr are also several thousand strong and completely avert this, and Lirael shows that the Abhorsens aren't quite as singular as first thought, the title character being the daughter of the previous Abhorsen herself and mothered by a Clayr.
• Lampshaded in Prelude to Foundation, where a noblewoman claims she should be the Empress because her family descends from an ancient ruling house. A nearby historian remarks that with said dynasty ruling 5,000 years ago, half of the galaxy is their descendants.
• Shea Ohmsford from the first Shannara was the last descendant of the great elven king Jerle Shannara. This was engineered—as Jerle had lived 500 years before and had three kids (plus two adoptive heirs), there were originally quite a few descendants of the Shannara line, but the Warlock Lord, knowing that they were the only people capable of wielding the only weapon that could kill him, made a point of hunting down and killing as many of them as he could find.
  • Zig-Zagged later in the series. Shea's two great-grandchildren opened up the Ohmsford line a bit, but was culled again by the time of The Voyage of the Jerle Shannara trilogy, and wouldn't start branching in different directions again until The Defenders of Shannara trilogy. Oddly, Jair is also said to be an ancestor of Wren Elessedil, which should mean the Ohmsford family expanded on through the Elessedils, but the text never treats this as if it is the case.
• Played Straight and averted in A Song of Ice and Fire:
  • The Starks, Tullys, and Baratheons are all confined to half a dozen or so members at the most, and the inheritances of their various regions are threatened because of it, while the former ruling Targaryen family is down to one (confirmed) member. Meanwhile, the Lannisters, Martells, Arryns, and Tyrells are all bursting with wide and diverse family trees, with mentions of separate family branches being established. Thicket or stalk, you can still find screwed-up in the Houses, though.
  • In the Starks' case, it may be partially justified as all of Lord Eddard Stark's siblings were killed or 'took the black' (joined the Night's Watch, a celibate order) before having children, though there is a distantly related House, the Karstarks. Even without sudden narrowing, Northern Houses as a whole do tend to be streamlined when compared to Southern ones... for good reason. The harsher the environment (the Eyrie certainly counts, too), the greater the chance you'll not find many cousins and cousins of cousins by blood. As, Winter is harsh: the superfluous, weak, or useless get regularly trimmed so the core may live through it. One way or another.
  • We do hear of the possibility in one book of a member of one noble House taking the name of another to prevent that House going extinct, so this may be why there are so few other branches.
  • The Targaryens tried keeping it in the family too much, but it's a common knowledge that there are many Targaryen descendants in Westeros, either illegitimate or through the female line. Aegon IV was such a gigantic casanova that it was said that he had slept with every woman in the Seven Kingdoms, so there are probably hundreds of illegitimate Targaryens lurking about. The Baratheons were actually founded as a cadet branch of the Targaryens, since their founder Orys Baratheon was a bastard son of Aerion Targaryen (father of Aegon I), and Robert, Stannis, and Renly Baratheon additionally have a much recent Targaryen ancestor in the form of their paternal grandmother, Princess Rhaelle (in fact, it's the reason why Robert managed to take the Iron Throne in the first place). They have also married fellow noble houses like the Penroses, Plumms, and Martells, which becomes a plot point in A Dance with Dragons. Even though the Blackfyres (descended from a legitimized bastard of Aegon IV) are extinct in the male line, the female line is rumored to have survived to the present day, and it's possible that the supposed "Aegon VI", the long-thought-to-be-dead son of Prince Rhaegar Targaryen, is actually a Blackfyre descendant.
• In Tales of the Branion Realm, the DeMarian royal family rarely has more than a dozen members while other noble families may have hundreds, but has nonetheless managed to survive for 900 years.
• In Harry Harrison's Tunnel Through the Deeps, the main character gets a lot of shit because he's descended from George Washington, whose rebellion failed in this world. Assuming anyone even still cared about a 200 year old rebellion (book set in 1973) that never had a follow up... there should be hundreds or even thousands in the Washington bloodline. But we only hear about our hero getting identified for it.
• Averted in Anne Rice's The Vampire Chronicles, where Maharet has been keeping track of the descendants of her human daughter since she became a vampire back in Ancient Egypt. The Great Family now has branches all over the world. However, for practical reasons and due to ancient traditions, Maharet only keeps track of her matrilineal descendants. Why? Because she can't be sure that her male descendants' children are really theirs. It's not clear whether she will change her methods with the introduction of reliable paternity tests.
• In Simon Hawke's The Wizard of novels, Billy Slade is the one and only descendant of Merlin Ambrosius.

Live-Action TV

• Charmed:
  • A rare female example. The Charmed Ones (Prue, Piper and Phoebe Halliwell) are three sisters who are the descendants of 17th-century witch Melinda Warren, who prophecied that three sisters descended from her would be the most powerful of all good witches. Apparently, up until the birth of the protagonists, there never were three daughters per generation. Which makes it odd that in one episode, the sisters witness their past lives who were three cousins and also part of the Warren-Halliwell family, so you would think that the cousins' mothers would have been three sisters. The family tree prop, which is seen in the background but never read from, has it that one of them was related through her father rather than her mother. But that contradicts Grandma Penny's statement that Wyatt was the first male born into the family. Some fans try to reconcile the Continuity Drift as Penny really meaning Wyatt was the first male with powers born into the family.
  • Kind of subverted in season 4 when we find out about their long-lost maternal half-sister Paige, who takes Prue's place as the third Charmed One after Prue's untimely death. But of course nobody had thought of her yet in season 1 when the trope was established. Unless you accept that there is no limit to the number of siblings in the Charmed Ones' generation as long as there are least three sisters. Otherwise providence would have to wait until the mother reached menopause to grant the powers to the sisters because more siblings might still be born. Besides we find out in "That '70s Episode" in season 2 that the sisters had their powers from birth — presumably because they were always going to be witches, it's just the Charmed gimmick that wasn't (and couldn't be) established until Phoebe's birth.
• Game of Thrones:
  • Played straight by many houses whose patriarchs seem to lack siblings. The Stark children of Winterfell have no cousins except Lord Robin Arryn of the Eyrie (the son of Lady Catelyn's sister Lysa) since Lord Ned's siblings all died (Brandon and Lyanna) or joined the celibate order called the Night's Watch (Benjen) before having children. Though they are very distantly related to House Karstark of Karhold, which descends from a younger son in the Stark line many generations ago.
  • Although in the finale of Season 6, it turns out that the Stark children's supposed half-brother, Jon Snow, is actually their cousin, being Lyanna Stark's son by Prince Rhaegar Targaryen rather than the bastard son of Ned Stark by an unknown mother as believed.
  • Averted by the Lannisters in earlier seasons; Lord Tywin (Lord of Casterly Rock, and father of Queen Cersei, Ser Jaime and Tyrion) is assisted by his younger brother Kevan, and Kevan's son Lancel is squire to King Robert.
  • Justified with the Targaryens, whose tradition of incestuous brother-sister marriages to maintain the purity of their Valyrian Dragon Rider blood limited the branching of the family tree, leaving them very vulnerable to a Succession Crisis.
  • As of the end of Season 6, this also happens to the Tyrells and Martells. Since several of their family members from the books had been Adapted Out, while the rest received Death by Adaptation, both houses are legally extinct, which leaves Lord Mace Tyrell's elderly widowed mother Olenna Tyrell (née Redwyne) and the Sand Snakes (Prince Oberyn Martell's eight bastard daughters) to rule the Reach and Dorne respectively. By the next season, they're all dead as well, leaving both regions leaderless. However, in the final season, Varys mentions a new Prince of Dorne who offers support for Daenerys' siege of King's Landing and who later appears in the Great Council at the Dragonpit, though as a total Canon Foreigner it's never made clear if he is a surviving member of House Martell or what.
• Love and Destiny: After her father's death Ling Xi is the last descendant of the Dan Bird tribe.
• In The Secret Circle, the coven are all descendants of six witch families (twelve in the books). How six families managed to intermarry for 300 years without inbreeding is a hefty bit of Fridge Logic at first. It's later explained that there are other witches and circles within Chance Harbor, allowing for new blood to enter the coven, and while the Circle is made of six witch families, the previous Circle contained twelve witches (a member from each of the families and their spouse).
• In the Star Trek: The Next Generation episode "Sub Rosa", we learn that a "ghost" named Ronin has been bedding Dr. Beverly Crusher's female ancestors for centuries, moving from mother to daughter, and is now moving onto Crusher following the death of her grandmother Felisa Howard. The logical flaws start with the fact that all her female ancestors were apparently named "Howard", indicating that Crusher is the first woman in her family to lose her maiden name, despite her living in the twenty-fourth century and the ancestor this started with living in the seventeenth century.^note It is established that the Howard family is from Scotland, where it was commonplace for women to keep their maiden names until the twentieth century. However, the premise is still logically flawed as it requires that the Howard women passed their maiden name on to their daughters. Not to mention what would happen if a Howard woman failed to produce a daughter - and in fact Beverly never had one (would Ronin have to move onto Wesley after Dr. Crusher died?).

Religion and Mythology

• Subverted trope in The Bible, of which it's commonly held that Jesus needs both a father and mother to both be descendants of the entire Davidic dynasty. Through his mother, he gets biological descent, and through his adoptive father who has direct male descent, he becomes legal heir (although Mary's descent is not explicitly stated). Not to mention that Jesus has several brothers (and there's a possibility that his cousins on his mother's side may also have the same descent).

Tabletop Games

• Averted in Legend of the Five Rings where the direct descendants of the two dozen or so gods and heroes that founded Rokugan number in the tens of thousands. And that's not counting the two million or so samurai that carry those gods' and heroes' names through fealty. It does appear in the first Imperial line, but only because when a new Emperor takes the throne, all of the other candidates must renounce their family name and be adopted into one of the secondary Imperial families. Interestingly, this does lead to the logical conclusion of the Imperial family being wiped out in the first story arc. An heir turns up Moses in the Bulrushes-style in the third arc... but he's the new Big Bad.
• Warhammer's Tyrion and Teclis have always been the only direct descendants of the first High Elf Phoenix King—Aenarion the Defender—from his oldest son Morelion over seven thousand years ago, and hence the direct inheritors of his bloodline and destiny. However, this trope was averted in the 7th edition High Elf army book (and the Tyrion and Teclis trilogy written afterwards) when it became clear that they're only the last surviving descendants, and the rest of Aenarion's heirs were systematically murdered by a Greater Daemon out for revenge against the bloodline of the elf who slew it. Given the extreme longevity and slow reproduction of elves, it helps that there have only been a handful of successive generations born during that time. They also have a several greats-half-uncle Malekith from Aenarion's second marriage, but he is unable to have children due to the burns he sustained from the Flame of Asuryan. The trilogy even has a character mention that if the vengeful Greater Daemon is out to kill descendants of Aenarion they're welcome to go after Malekith.
  • The elves also maintain the tradition of the Everchild, an intentional attempt to preserve the female line of descent from Aenarion's first wife Astarielle and daughter Yvraine. Unknown to pretty much everyone, the current one is also Tyrion's illegitimate daughter (The idea being that every Everqueen is supposed to be the daughter of a Phoenix King to symbolize the union of the two crowns).
  • Played straight during The End Times scenario when the character Volkmar the Grim is revealed to be the last blood heir of Sigmar, who disappeared from human lands 2500 years earlier. Unlike with the elves, no slow generation time, ancient daemons with a grudge or bloodline breeding programme is involved, and Sigmar was known to have neither married nor sired children (The novels would reveal that Sigmar did have at least two illegitimate children, but they were never publicly acknowledged as such - Sigmar himself didn't know he was their father until they were teenagers), which is why The Empire has an Elective Monarchy in the first place.
• Downplayed Trope in Sentinels of the Multiverse. Legacy is a Legacy Character who has always passed his powers to his firstborn, who even picked up an extra power. While any Legacy can have several children, and some did, only the first child will be a Legacy. America's Newest Legacy is the first female Legacy. In one timeline, this trope and her death turned Legacy into Fallen Hero Iron Legacy, as since there would no longer be a Legacy after his death, Legacy snapped and decided to eliminate evil before his death by any means necessary, no longer caring for collateral damage and becoming a Hero Killer, having killed Bunker, Unity, Mr Fixer...

Video Games

• Averted in the Assassin's Creed series, where Ezio and Altair are from different parts of Desmond's family tree, and Ezio is known to have at least one descendant Clay Kaczmarek, aka Subject 16 who is from an illegitimate child. And then there's Connor Kenway (AKA Ratonhnhaké:ton), who is half-Mohawk, another ancestor unrelated to the other two. Word of God also explains that they were intentionally averting this trope.
• Averted all over the place in Blaze Union. Medoute, the descendant of Gill the legendary dragonslayer, mentions repeatedly that she's from the secondary line. Characters also discuss that due to the Imperial bloodline being so diluted and spread throughout the people, it's not unusual for children qualifying as Brongaa's descendants to be born in all walks of life; the interesting thing about Gulcasa is that he's the first pureblood to be born in centuries.
• In the Castlevania series, only the Belmont family has the power to vanquish Dracula when he rises every 100 years (though there have been many exceptions). Each time he rises, there are only one or two Belmonts around to do the job.
  • The Morrises, a family that stepped up to the plate to battle Dracula when the Belmonts went missing, are said to be related to the Belmonts. The relation isn't pure, however, and they aren't able to effectively wield the Vampire Killer whip without significant cost to themselves.
  • Exception: The plot of the mobile game Castlevania: Order of Shadows involves three Belmont siblings, two of them women. But only the guy gets to take on Dracula, and the game isn't considered canon anyway.
    • It is stated that the villagers in Castlevania: Order of Ecclesia are of the Belmont lineage, but don't have their last name.
    • The Renards are also distantly related to the Belmonts.
• Done in Chrono Trigger, where only the Royal Family of Guardia is said to be descended from Ayla and Kino, ancestors some 65 million years back. Then again, over the course of 65 million years, pretty much everyone can trace their lineage to them at some point.
• Dragon Quest:
  • Subverted in Dragon Quest V, where whichever of the two/three (depending on the version) available brides the main characters marries becomes the mother of the hero destined to put on the Zenithian gear and destroy the Big Bad. The children themselves all have the same personality regardless of their mother not too surprising considering they only met their mother and father almost a decade later and after de-statueing them, only taking her hair color (blond, blue or black).
  • In Dragon Quest VIII, the Big Bad is tracking down the descendants of the Seven Sages who originally sealed him away, as their deaths are the only way to release his original body. The game establishes that only one descendant in each most recent generation is the heir (as Jessica's brother Alistair held the bloodline whereas Jessica just received magical strength), with an odd exception in the case of Marta; while she had a son, he decided to practice medicine in a nearby town, figuring his skills would be put to better use there, and forfeited his status as an heir in the process (which managed to throw the Big Bad off for a bit).
• In Dragalia Lost, the player character Euden's dragonblood is shared with his siblings. However, the will of their ancestor, Alberius, is only truly passed to him, and Euden is seen as the direct descendant. His siblings end up joining forces with the Big Bad, Morsayati.
• In The Elder Scrolls IV: Oblivion, the realm is protected from Mehrunes Dagon by Dragonfires, product of an ancient pact. At the time of the game, the last Septim Emperor is assassinated, laying the realm open to invasion by the Daedric forces. The main plotline of the game involves finding the hidden son of the last Septim and getting him the Phlebotinum he needs to start the Dragonfires again. The murdered Emperor had three other sons, all of whom were taken out in similarly nefarious assassinations shortly before the game begins (making the Blades the worst bodyguards in history). Martin survived because, as the bastard son of the Emperor, his existence was kept so secret that even he didn't know who he was. It does not address, however, the fact Uriel's sons were in their 50s and would have had their own heirs, who could well have had some of their own as well. Or Uriel's siblings and nephews. Or any female Septims.
  • The backstory, however, averts this. The main Septim line already had had various winnowing events or outright going extinct. Mostly it just led to another branch becoming the main Septim line with the Elder Council's blessing and continuing the overall Septim line of Emperors (in one case, for example, a cousin supposed to be more closely related to Tiber Septim took over).
• Inverted in Fable III, only the youngest of the Hero of Bowerstone's two children gets any Hero powers.
• In Final Fantasy VII, Aerith's birth mother Ilfana is the last pure-blooded Cetra on the planet, Aerith herself having a human father. The implication is that the remaining Cetra descendants either died out or were absorbed into the human population.
• Fire Emblem:
  • In Fire Emblem: Genealogy of the Holy War and Fire Emblem: Thracia 776, Holy Blood is passed down from the 12 Crusaders to their descendants in two variations: minor and major Holy Blood. Word of God explains that whether the child of someone with "major" blood (who are uniquely able to use the Crusader's Ancestral Weapon) gets "minor" (just some stat bonuses) or "major" blood is completely random (birth order and sex play no part) and that the blood can be determined by a birthmark. From the cast of the games, it seems as though only one major blood carrier of each line is possible per generation despite the player's ability to arrange it so that there are three major Od carriers in the second generation. Which is ironic, as that that's not even counting Galzus and Mareeta, who has brands on their bodies, implying that they are major Od carriers.
  • Seemingly averted in Fire Emblem: Awakening, as the descendants of Ylisse's first Exalt (who in turn was descended from Marth) all bear the Brand of the Exalt, and those with the Brand can both wield the Falchion and perform the Awakening Ritual. Chrom's younger sister Lissa does not have the Brand, having her fear that she was a bastard child, but the fact that her Kid from the Future Owain has it, while proving Lissa is really a member of the royal family, raises questions about why hers never surfaced. Also, in Lucina's Support conversations with whomever her sibling is, it is covertly revealed that they can wield Falchion as well, but they never can do it in-game due to Gameplay and Story Segregation. In turn, in Fire Emblem Fates, Owain (under his alias Odin) passes on the Brand to his own child(ren).
  • In Fire Emblem: Three Houses, much like in Genealogy and Thracia, several lines of nobility and royalty are descended from the 10 Elites and Four Saints, heroes of the continent of Fódlan’s ancient past, though only a select few of these descendants inherit a Crest (existent in both minor and major variants), a special power and the ability to wield the bloodline’s Ancestral Weapon without suffering dangerous penalties to one’s health^note in-game, if a unit without the Crest matching a particular weapon uses it, they’ll take damage at the end of a combat round and suffer heavy stat penalties, or risk transforming into a grotesque monster. It’s mentioned that the bloodlines are thinning to the point where descended nobles have to try several times to have a single Crest bearer per generation, and that rare status makes Crest bearers hotly valued commodities for their families and those seeking to raise their status by marrying into a Crest bloodline.
• The Legend of Zelda:
  • In The Legend of Zelda: A Link to the Past and The Legend of Zelda: Four Swords Adventures, Link is a descendant of ancient heroes. Made more explicit in Twilight Princess, where that game's Link is directly descended from the Hero of Time.
  • The royal Zelda line has only ever been depicted with a single child per generation, who inherits the name Zelda and the powers of their goddess ancestor Hylia. The one exception is in Zelda II: The Adventure of Link, in which the backstory concerns Zelda's brother.
• In The Lost Crown, William Ager was a villainous example. Unusual in that he died of tuberculosis with no heir to pass on the family secrets to, hence let down both Destiny and centuries of bloodthirsty tradition.
• In Mark of Kri, the marks are passed down through the firstborn descendants of six separate families, one mark per family, with at least two of the families having willingly died out to prevent their marks from being passed down any further. In an interesting turn of events, however, it is The Hero's younger sister who bears the mark, even though he is the firstborn, though the second game hints that they may not actually be related.
• One of the conversations in Poker Night 2 reveals that Brock Samson of The Venture Brothers is one of only two descendants of Ash Williams's one-night stand with Sheila back in the 13th century. Of course, it could be just GLaDOS messing with them.
• Also averted in Tales of Symphonia, where the family of the Chosen is huge, has many branches, and is scattered all over the world so that if something happens to one branch, the bloodline will still exist.
• What Remains of Edith Finch has the Finch family, who suffer from a maybe-real-but-maybe-not family curse that gives them a rather high mortality rate. While every generation of Finches had more than one child, only one child per generation would ever survive long enough to reproduce, thus maintaining a single line of descent. The exception being Player Character Edith herself, who only has one child because she dies giving birth to him at the end of the game. Her brother Milton also may or may not have deliberately isekai'd himself and had a child of his own as the King from The Unfinished Swan. If he did, then the single line of descent is broken and possibly the curse along with it, if it's real.

Webcomics

• Parodied in The Adventures of Dr. McNinja, where a demon can only be slain by one of "pure Belstein blood". There is only one left, who's deformed and in a wheelchair due to generations of inbreeding.
• Digger: Inverted and lampshaded when the ghost of the long-dead wombat Helix immediately pegs Digger as a descendant:
  Digger: Isn't that a little... improbable?
  Helix: I had eight sons. A thousand years ago. You do the math.
• Girl Genius.
  • Subverted with the lineage of the Storm King. Part of the plan of Zola (the fake Heterodyne) is to ally with and marry a direct descendant of Andronicus Valois, the Storm King. When Gilgamesh skeptically points out that, if the legends are true, half of Europe is descended from the Storm King, she angrily specifies that it's a descendant who the Fifty Noble Families of Europe will recognize. Later, when she explains more of the plan to him, she specifies why this one's confirmed, and it has something to do with the Mongfish family being specially gifted in the biological sciences.
  • Played straight with Agatha. While the past (almost always male) Heterodynes had no problem with assembling large harems, the family also tended to infuriate the neighbors on a regular basis. Sparks in general also tend to mess with and create very dangerous things.

Western Animation

• Dragons: The Nine Realms: Tom and Olivia are the only known descendants of Hiccup's and Astrid's line.
• Ninjago provides two examples:
  • Lloyd is the only descendant of Garmadon and the latest in the line of the First Spinjitzu Master.
  • Cole is the last descendant of the Elemental Master of Earth during the Serpentine War.
• Star vs. the Forces of Evil: Main character Star Butterfly is the sole heir of the royal Butterfly family which has ruled over Mewni for centuries. This is later zig-zagged when it turns out she isn't actually a descendant of the founder of the family line but rather Festivia who was made queen as a baby as part of a cover-up. As such, when she gives up her power to the orginal queen Eclipsa she is no longer the heir to the Kingdom of Mewnie. However, this still means her family had ruled over Mewnie for centuries and includes prominent figures such as her mother Moon Butterfly.
• Steven Universe: Steven is Roses only child. Justified as she had to give up her physical form to give birth to him.
• Tabaluga: The protagonist Tabaluga is the only son of Tyrion, the former protector and king of the fictional land of Greenland.

Real Life

• Enforced in China by the government's one-child policy, to keep the already humongous population from completely exploding. It's been estimated that without this policy, there would be 400 million more Chinese people. However, ethnic minorities were exempted, and people who lost their child were allowed to have another. People also widely got around it by abandoning children (most are girls) or killing them. Now the government has scrapped the policy, fearing it went too far with a lopsided sex ratio.
• The Kingdom of Jerusalem experienced this for four generations of Kings and Queens during the thirteenth century. With the death of the King of Jerusalem Conradin, the line of his great-great-grandparents Isabella I and her second husband Conrad of Montferrat became extinct, thanks to their daughter Maria of Montferrat and her descendants only having one surviving child each^note Maria was likely born after her father’s death, and both her and her daughter Isabella II suffered Death by Childbirth. Isabella II did have a child before her son Conrad but the child died in infancy. This caused a succession dispute between two of Conradin’s half-second cousins once removed as the closest living relatives with a claim to Jerusalem.
• This trope is seriously averted with Genghis Khan: about 0.5% of the male population of Earth descends directly from Genghis Khan or his male relatives. Douglas Adams spoofs this in The Hitchhiker's Guide to the Galaxy.
  • Not a spoof at the time, as the true scope of Genghis's genetic legacy didn't come to light until after Adams passed away. He was just making a funny contrast between Prosser and the Great Khan. That makes this Hilarious in Hindsight.
  • Also, the book specifies that he was a "direct male-line descendant" of Genghis Khan, apparently meaning the more improbable lineage in which the long chain from Prosser to Genghis Khan consists only of men.
  • Actually, the above-mentioned study was of Y-chromosomes. 1 in 200 people in the world are descended in direct male-line descent from the same man in Asia some 1000 years ago or less, and the rather strong conjecture is that it was Genghis Khan, as his descendants conquered (and raped) much of the continent.
  • Some 30% of Europeans have Charlemagne, or Charles the Great, as their ancestor. Charles was not a first-class fornicator; he had five wives (two marriages were annulled, three wives predeceased him) and five concubines, but he never had more than one wife and one concubine at a time, and he doesn't seem to have done much outside those relationships. However, he had eighteen children, of whom all but two or three survived childhood, and most in turn had children—many of whom were illegitimate and therefore ended up having descendants marrying into the lower nobility or the ranks of the commoners sooner rather than later.
• This is averted with pretty much anyone who had descendants if you go surprisingly not far back in history. A paper in Nature demonstrated that if a person has four or five grandchildren, either their line tends to die out within a few generations, or the number of descendants begins to increase exponentially. Someone living two or three thousand years ago will either have no descendants at all alive today or be an ancestor to a lot of people.
• Averted with Sophia of Hanover who has over 5000 legitimate descendants. Out of these, all who are not Catholics or married to Catholics (still over 1000) are in line to the British throne.
  • Because the members of European royal families tended to marry members of other European royal families, just about every royal in Europe is descended from her.
  • Because her descendants were mostly royalty, and that royal men tend to have at least one mistress, there are even more illegitimate descendants. William IV of the UK alone had ten illegitimate children by his mistress, the actress Dorothea Jordan (he would have married her, but there would have been an uproar; remember Edward VIII? Now put that a hundred years earlier). Among those illegitimate descendants is David Cameron.
• When it comes to European royalty, the grand champion of averting this trope might well be Edward I of England (the legendary "Edward Longshanks" of Braveheart fame), who lived between 1239 and 1307 and fathered sixteen children, nearly all of whom survived into adulthood and had children themselves. According to genealogists who have studied his family line, the man now has close to four million living descendants around the world (most of them are in the United States, Canada, and Brazil of all places). Apparently^note According to Mark Humphrys, this claim has no adequate proof all U.S. Presidents except for Martin Van Buren are descended from him.
• Sometimes intentionally attempted by dynasties to limit the number of people vying for the throne, land, or fortune. Different cultures handled this in different ways:
  • In Europe, this often came in the form of sending surplus sons off to monasteries and various church jobs, ensuring no legitimate children. Alternately, younger sons would be sent to the army, where they would fight (and in many cases hopefully die on the battlefield); this, incidentally, is where we get the term "cadet" for a trainee officer ("cadet branch"=junior line of a noble house). If the line were about to expire, a monk or priest in such a position might be permitted to leave the Church and marry. That's where Münchhausen's last name comes from, BTW.
  • In Ancient Mesopotamia, aristocratic sons could end up as castrated but high-ranking officials at court. The Chinese sometimes did much the same thing.
  • In the Ottoman Empire, the successor was entitled to have all his brothers and half-brothers strangled upon being chosen.
  • Royal relatives in Ethiopia used to live in Gilded Cage prisons on top of high buttes in the wilderness, to ensure their genetic lines remained strictly under the reigning monarch's control.
  • One reason why royal entourages in Ancient Egypt were so enormous was that a ruling Pharaoh needed to keep all of his female relations on a tight leash because the divine grace of rulership was passed down through the female line. Thus, every Pharaoh's court was awash with his own and his Great Wife's sisters, aunts, female cousins, daughters of his predecessors' junior wives, etc, none of whom could be allowed to marry without rock-solid guarantees of their would-be spouse's loyalty.
  • The Hapsburgs of Austria and Spain tried keeping it in the family. The last member of the Spanish line, Charles II, ended up being saddled with a truly depressing array of mental and physical disabilities and was probably sterile to boot, so it's safe to assume they didn't exactly find the winning formula, either; his death led to the War of the Spanish Succession that ultimately led to Spain passing out of Habsburg hands and into those of their rivals, the Bourbons. His sister Margaret Theresa was fairly normal, but only one of her children (that she had with her uncle to boot) survived, and said daughter Maria Antonia had a Death by Childbirth, with her son Joseph Ferdinand dying at six. (Whether this a result of inbred health problems or an assassination is still up in the air.)
  • In Japan, the 1947 revision of the Imperial House Law made all the collateral lines of the Imperial family into commoners — if you're not a direct-line descendant of Emperor Hirohito or one of his brothers, you aren't a possible candidate for the Chrysanthemum Throne. Female children in the Imperial family are also required to become commoners once they marry, so none of their children are candidates. Oh, and that revision also banned adoption of an heir into the Imperial family (one way the main Imperial family used to tap the manpower pool of the collateral lines). Which means as of 2023, the Japanese dynasty is now resting on the shoulders of a 16-year-old boy, as the only possible heir young enough to produce more heirs.

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