History Main / SingleLineOfDescent

* ''Literature/TheFallOfTheHouseOfUsher'' is a classic example, as the Usher family is described as having produced no side-branches and declined to the point that only two siblings remain.

** 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. (He ''does'' meet a first cousin at one point, but she's explicitly from the maternal, non-royal, side of his family.) 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".

* In ''Film/{{Underworld}}''. The [[OurWerewolvesAreDifferent 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 SingleLineOfDescent.

* ''Literature/DeltoraQuest'' 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 [[EvilChancellor Evil Chancellors]] secretly working for the Shadow Lord, in order to set up the loss of power of the Belt. [[spoiler: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 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 the {{anime}} ''Manga/BlueSeed'' there was only one (well, two) people left of a bloodline whose lifeforce could destroy the DemonicInvaders.
* ''Anime/{{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.[[spoiler: His mother is the queen of Mu.]]

[[folder:Fanfiction]]

* ''The Fall of the House of Usher'' is a classic example, as Poe describes them as having produced no side-branches and declined to a point where only two siblings remained.

* ''LightNovel/UndefeatedBahamutChronicle'' 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 [[spoiler: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.]]

** The royal Zelda line has only ever been depicted with a single child, who inherits the name Zelda and the powers of their goddess ancestor Hylia. The one exception is in ''VideoGame/ZeldaIITheAdventureOfLink'', in which [[AllThereInTheManual the backstory]] concerns Zelda's brother.

* In ''VideoGame/TheLegendOfZeldaALinkToThePast'' and ''VideoGame/TheLegendOfZeldaFourSwordsAdventures'', Link is a descendant of ancient heroes. Made more explicit in ''[[VideoGame/TheLegendOfZeldaTwilightPrincess Twilight Princess]]'', where that game's Link is directly descended from [[VideoGame/TheLegendOfZeldaOcarinaOfTime The Hero of Time.]]

* ''Literature/DeltoraQuest'' 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. [[spoiler:This was enforced by the Shadow Lord to cause the loss of the power of the belt. It's eventually subverted, as Adin had multiple children who also did. By the present day, there are enough potential heirs if you know where to look for them to make wiping out the royal line an impractical strategy.]]

** In the Starks' case, it may be partially justified as all of Lord Eddard Stark's siblings were killed or took the Black before having children, though there are a distantly related branch, 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, [[HostileWeather Winter]] is harsh: the superfluous, weak, or useless get regularly trimmed so the core may live through it. [[ReassignedToAntarctica One]] [[BetterToDieThanBeKilled way]] [[YouHaveOutlivedYourUsefulness or]] [[MercyKill another]].

** A rare female example. The Charmed Ones 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 ContinuityDrift as Penny really meaning Wyatt was the first male with powers born into the family.

** A rare female example. The Charmed Ones 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 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 ContinuityDrift as Penny really meaning Wyatt was the first male with powers born into the family.

** A rare female example. The Charmed Ones 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 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 it as Penny really meaning Wyatt was the first male with powers born into the family.

* In the ''Series/StarTrekTheNextGeneration'' episode "Sub Rosa", we learn that a "ghost" named Ronin has been bedding Dr. 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.[[/note]] Not to mention what would happen if a Howard woman failed to produce a daughter (would Ronin have to move onto [[CreatorsPet Wesley]] after Dr. Crusher died?).

** As of the end of Season 6, this also happens to the Tyrells and Martells. [[spoiler:Since several of their family members from the books had been AdaptedOut, while the rest received DeathByAdaptation, 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 CanonForeigner it's never made clear if he is a surviving member of House Martell or what]].

** Played straight by many houses whose patriarchs seem to lack siblings. The Stark children have no cousins except Robin Arryn since Ned's siblings all died or took the black before having children, though they are very distantly related to the Karstarks.
** Averted by the Lannisters in earlier seasons; Lord Tywin is assisted by his brother Kevan and Kevan's son Lancel is squire to King Robert.
** Justified with the Targaryens whose tradition of incest limited the branching of the family tree, leaving them very vulnerable to a SuccessionCrisis.
** As of the end of Season 6, this also happens to the Tyrells and Martells. [[spoiler: Since several of their family members had been AdaptedOut while the rest received DeathByAdaptation, both houses are legally extinct which leaves Olenna Tyrell (nee Redwyne) and the Sand Snakes (Oberyn'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 ''Prince'' of Dorne who offers support for Daenerys' siege of King's Landing, though it was never cleared if he is a surviving member of House Martell]].

** Kind of subverted in season 4 when we find out about [[LongLostRelative their long-lost 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.

** Kind of subverted in season 4 when we find out about [[LongLostRelative Paige]]. 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 as long as there is at 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.

** A rare female example. The Charmed Ones are three sisters who are the descendants of 17th-century witch Melinda Warren. 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 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 it as Penny really meaning Wyatt was the first male with powers born into the family.

** A rare female example. The Charmed Ones are three sisters who are the descendants of 17th-century witch Melinda Warren. 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 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.

** A rare female example. The Charmed Ones are three sisters who are the descendants of 17th-century witch Melinda Warren. Apparently, up until the birth of the protagonists, there never were three daughters per generation.

Similarly, the sole true descendant is generally treated as essentially [[IdenticalGrandson 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...).

Similarly, the sole true descendant is generally treated as essentially [[IdenticalGrandson 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.

* 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.

** The Hapsburgs of Austria and Spain tried [[KissingCousins 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 UsefulNotes/WarOfTheSpanishSuccession 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 DeathFromChildbirth, 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.)

** 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 they are so few other branches.

** 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 2021, the Japanese dynasty is now resting on the shoulders of a 14-year-old boy, as the only possible heir young enough to produce more heirs.

Note that, in the present generation, if there is another sibling, he or she tends to be recruited by the BigBad as the EvilCounterpart.