History Main / HereditaryTwinhood

[[folder:Films -- Animation]]
* ''WesternAnimation/BarbieInTheTwelveDancingPrincesses'': Some of the [[MassiveNumberedSiblings twelve sisters]] are the result of multiple births: Hadley and Isla are twins, and Janessa, Kathleen and Lacey are triplets. [[ThoseTwoGirls Delia and Edeline]] are also implied, though not explicitly stated, to be twins.
[[/folder]]

* ''Film/{{Twins}}'': At the end, the twin brothers have married twin sisters, and each couple has twin babies.

** Phoebe also counts, since she has a twin sister named Ursula and herself gave birth to triplets (serving as a surrogate mother for her brother and his wife).

* The Derrico family of ''Doubling Down with the Derricos'' has a total of 14 children, and of those there are two sets of twin boys, a set of quintuplets (three girls and two boys), and triplets (two girls and a boy).

* A town in Brazil called [[https://en.wikipedia.org/wiki/Cândido_Godói Candido Godói]] is notorious for an unusually high rate of twins, which itself is '''10%''', causing people left and right to be baffled. The most explanatory hypothesis for this reason is local genetic traits. It has been reported that twin births were particularly noted when the first immigrants of the town, which happened in the early twentieth century, included ''seventeen'' sets of twins. On top of all that, the population can trace their ancestry to the Hunsbrück region of Germany, which ''also'' has a higher than average twinning rate.

* ''Film/GodzillaKingOfTheMonsters2019'': Dr. Ilene Chen, Monarch's chief mythologist and resident MsExposition, not only has a twin sister, but also twin daughters, her mother and aunt are twins and her grandmother and great-aunt are twins. The novelization takes this even further, confirming that twins run in Ilene's family. WordOfGod reveals that this is meant to settle Ilene and her sister Ling into the roles of the Shobijin, Mothra's twin priestesses.

** Taken UpToEleven in another FlashForward episode, "[[Recap/TheSimpsonsS23E9HolidaysOfFuturePassed Holidays of Future Passed]]". Apu and Manjula are briefly shown with their now adult octuplets, who themselves each had a set of octuplets.

** Jason himself [[spoiler:fathers fraternal twins with Polly--Juniper and Dagwood]]. Cheryl attributes this to twins running in the Blossom genes, even though this would be dependent on the mother's genes, not Jason's.

* ''Series/SabrinaTheTeenageWitch'': The "Family Secret" that Sabrina has to learn to earn her Witch's License is that every member of the Spellman family is born with a twin, and one of them is inevitably the EvilTwin, who will be imprisoned in the Twin Cities in the Other Realm. Sabrina's twin is named Katrina, and there's a series of tests to determine which one of them is evil (foregone conclusion: it's Katrina). However, the "twins" are not actually siblings but inexplicably identical relatives from different branches of the family.

* Helena and Sarah on ''Series/OrphanBlack'' are revealed to be identical twins in a group of identical clones--their embryo split into two. Helena then carries twin boys of her own later in the show.

* ''Series/WandaVision'' uses "twins begetting twins" for a different kind of plot twist. Wanda is a twin and gives birth to twin sons when she had just been expecting one child. But [[spoiler:seeing her sons reminds her of her brother, who had gone unmentioned since his death -- which in turn causes the fragmented sitcom reality to unravel]].

* ''Series/SabrinaTheTeenageWitch'': The "Family Secret" that Sabrina has to learn to earn her Witch's License is that every member of the Spellman family is born with a twin, and one of them is inevitably the EvilTwin. However, the "twins" are not actually siblings but inexplicably identical relatives from different branches of the family.

** [[spoiler:Their father Clifford]] is revealed to have a long-lost twin brother in season 2.

* ''Series/SabrinaTheTeenageWitch'': The "Family Secret" that Sabrina has to learn to earn her Witch's License is that every member of the Spellman family is born with a twin, and one of them is inevitably the EvilTwin.

* ''Series/DesperateHousewives'': Lynette and Tom have twins Porter and Preston at the beginning of the series. So when Lynette has a SurprisePregnancy in Season 5, she gets pregnant with twins again, although one of them dies in utero.

In real life, there is no scientific proof that twins skip a generation, and as far as scientists know, identical twins are a spontaneous, random occurrence that doesn't run in families. Fraternal twins can run in the family, but only through the ''mother'': some women are genetically predisposed to hyperovulation[[note]]Fraternal twins are caused by two separate eggs being fertilized by two separate sperm, while identical twins are caused by a previously-fertilized ovum splitting in half. If a woman has a hereditary predisposition to ovulate more than one egg at a time, her chances of having fraternal twins will be higher, whereas the father's DNA obviously won't affect how many ripened eggs his partner has available for his sperm to fertilize[[/note]]. Artificial insemination and a previous birth can also increase the chances of a multiple birth. Fiction, however, will often treat [[AlwaysIdenticalTwins identical twins and fraternal twins similarly]].

In real life, there is no scientific proof that twins skip a generation, and as far as scientists know, identical twins are a spontaneous, random occurrence that doesn't run in families. Fraternal twins can run in the family, but only through the ''mother'': some women are genetically predisposed to hyperovulation[[note]]Fraternal twins are caused by two separate eggs being fertilized by two separate sperm, while identical twins are caused by a previously-fertilized ovum splitting in half. If a woman has a hereditary predisposition to ovulate more than one egg at a time, her chances of having fraternal twins will be higher, whereas the father's DNA obviously won't affect how many ripened eggs his partner has[[/note]]. Artificial insemination and a previous birth can also increase the chances of a multiple birth. Fiction, however, will often treat [[AlwaysIdenticalTwins identical twins and fraternal twins similarly]].

In real life, there is no scientific proof that twins skip a generation, and as far as scientists know, identical twins are a spontaneous, random occurrence that doesn't run in families. Fraternal twins can run in the family, but only through the ''mother'': some women are genetically predisposed to hyperovulation[[note]]Fraternal twins are caused by two separate eggs being fertilized by two separate sperm, while identical twins are caused by a previously-fertilized ovum splitting in half. If a woman has a hereditary predisposition to ovulate more than one egg at a time, her chances of having fraternal twins will be higher, whereas the father's DNA obviously won't affect how many ripen eggs his partner has[[/note]]. Artificial insemination and a previous birth can also increase the chances of a multiple birth. Fiction, however, will often treat [[AlwaysIdenticalTwins identical twins and fraternal twins similarly]].

In real life, there is no scientific proof that twins skip a generation, and as far as scientists know, identical twins are a spontaneous, random occurrence that doesn't run in families. Fraternal twins can run in the family, but only through the ''mother'': some women are genetically predisposed to hyperovulation[[note]]Fraternal twins are caused by two separate eggs being fertilized by two separate sperm, while identical twins are caused by a previously-fertilized ovum splitting in half. If a woman has a hereditary predisposition to ovulate more than one egg at a time, her chances of having fraternal twins will be higher, whereas the father's DNA obviously won't affect how many ripe eggs his partner has.[[/note]]. Artificial insemination and a previous birth can also increase the chances of a multiple birth. Fiction, however, will often treat [[AlwaysIdenticalTwins identical twins and fraternal twins similarly]].

In real life, there is no scientific proof that twins skip a generation, and as far as scientists know, identical twins are a spontaneous, random occurrence that doesn't run in families. Fraternal twins can run in the family, but only through the ''mother'': some women are genetically predisposed to hyperovulation[[note]]Fraternal twins are caused by two separate eggs being fertilized by two separate sperm, while identical twins are caused by a previously-fertilized ovum splitting in half. If a woman has a hereditary predisposition to ovulate more than one egg at a time, her chances of having fraternal twins will be higher[[/note]]. Artificial insemination and a previous birth can also increase the chances of a multiple birth. Fiction, however, will often treat [[AlwaysIdenticalTwins identical twins and fraternal twins similarly]].

In real life, there is no scientific proof that twins skip a generation, and as far as scientists know, identical twins are a spontaneous occurrence. Fraternal twins can run in the family through the ''mother'': some women are genetically predisposed to hyperovulation[[note]]Fraternal twins are caused by two separate eggs being fertilized by two separate sperm, while identical twins are caused by a previously-fertilized ovum splitting in half[[/note]]. Artificial insemination and a previous birth can also increase the chances of a multiple birth. Fiction, however, will often treat [[AlwaysIdenticalTwins identical twins and fraternal twins similarly]].

* ''WesternAnimation/GravityFalls'': Dipper and Mabel are HalfIdenticalTwins, which foreshadows the reveal that [[spoiler:their Great-Uncle Stan is an identical twin.]]

* ''ComicBook/YoungAvengers'' has a complex example. ComicBook/ScarletWitch is the fraternal twin of ComicBook/{{Quicksilver}}, and Speed is the reincarnation of one of her magically-conceived identical twin sons. In one BadFuture, ComicBook/KateBishop is pregnant with Speed's twins.

The presence of established twin relatives, identical or fraternal, can often set up the birth of more twins or a [[LongLostRelative long-lost twin]] showing up. If one of the parents is a twin, having twin children is often used to bring their story full circle (especially if the children are [[UntoUsASonAndDaughterAreBorn a male/female pair]]). Often, the newer or younger set of twins parallels the older one in some way: they bear [[GenerationXerox strong similarities to the previous set]], take different life paths, or have an entirely different sibling relationship.

* In ''{{Literature/Another}}'' twins run in the Misaki family. Besides Mei and her SeparatedAtBirth twin sister Misaki their birth mother Mitsuyo was also a twin, and Mei was adopted by Yuikyo, the other sister, after she suffered the TragicStillbirth of her own child and financial problems in Mitsuyo's family meant they couldn't afford to care for two children.

* ''WesternAnimation/BarbieInTheTwelveDancingPrincesses'': Some of the [[MassiveNumberedSiblings twelve sisters]] are the result of multiple births: Hadley and Ilsa are twins, and Janessa, Kathleen and Lacey are triplets. [[ThoseTwoGirls Delia and Edeline]] are also implied, though not explicitly stated, to be twins.

* In ''VisualNovel/FateHollowAtaraxia'' the Edelfelt family of magi has a unique bloodline ability that lets two members inherit the family's magic crest at once. During the third Holy Grail War the Edelfelt sent twin sisters to represent the family, and in the present day Luviagelita also has a twin sister.