History Sandbox / WorldOfOnlyChildren

** Steve Rogers (Comicbook/CaptainAmerica) was an only child. [[spoiler:The Paradise-X storyline shows he just wasn't aware of an older sibling...]]
*** As was his archnemesis, the Comicbook/RedSkull (probably due to his mother dying in childbirth and his father killing himself immediately afterwards). Red Skull's daughter Sin is also an only child.
** Matt Murdock (Comicbook/{{Daredevil}}) is an only child.

** Bruce Banner (Comicbook/TheIncredibleHulk) is an only child, as is his cousin Jennifer Walters (Comicbook/SheHulk), his wife Betty Ross (Red She-Hulk), and his father-in-law Thunderbolt Ross (ComicBook/RedHulk).
** Tony Stark (Comicbook/IronMan) is an only child [[spoiler:except for the brother he never knew about.]]
** All the original Comicbook/{{Runaways}} are only children, but this is justified because each set of parents agreed to give their designated place in paradise to their offspring. Because there were only six places, the six couples had one child apiece. [[SixthRanger Victor]] is an only child for [[RidiculouslyHumanRobots obvious reasons]]. The same can't be said for Xavin and Klara, but then again, it's never been explicitly stated that they didn't have siblings back on Tarnax VII or in 1907.
** Peter Parker (Comicbook/SpiderMan) is an only child--in his case, his parents had disappeared when he was a little kid (usually around the age of 4 to 6), so they didn't really get the chance to have another kid. And in the case of Peter's Aunt May and Uncle Ben, they (similar to Superman's adoptive parents) are sometimes portrayed as having been unable to have children of their own thru biological means.

** Notably averted with [[Comicbook/XMen the Guthries]]. [[MassiveNumberedSiblings All twelve of them]].
** ''ComicBook/YoungAvengers'': [[Characters/HawkeyeKateBishop Kate]] has an older sister, and it's implied that Eli comes from a large family. Billy and Tommy are twin brothers...via reincarnation (it's complicated). Billy mentioned he had two little brothers in the first arc, but over a decade later they've failed to appear in any capacity whatsoever. Teddy is an only child, which isn't too surprising given his parents were on opposite sides of an interstellar war. Same goes for Cassie, as her parents have split up and her father was [[DeathIsCheap dead for a while.]]

** Hermione Granger was originally intended to have a Muggle sisters. However, Creator/JKRowling struggled to find a way to keep her involved with the story from home and eventually gave up on her altogether, leaving Hermione an only child.

* From 1979-2016, UsefulNotes/{{China}}'s one-child policy prevented urban married couples from having more than one child[[note]]With numerous exemptions, such as: you can have two kids if you live abroad, if you've divorced and remarried, or if you're an ethnic minority.[[/note]]. This has led to coinage of the term [[http://en.wikipedia.org/wiki/Little_Emperor_Syndrome Little Emperor Syndrome]] to describe the social implications of such a phenomenon when it has an effect on a nationwide level. The law was slowly walked back over time, first couples where both spouses were only children could have two, then if one spouse was, and now all couples can have two children.
** It's also led to a fairly significant gender disparity; sons have always been more desirable than daughters, and all the more so when a couple is only allowed one child, so many parents aborted female fetuses or gave daughters up to orphanages to be put up for adoption so they could have a boy. At the moment, there are [[https://www.nytimes.com/2017/02/14/world/asia/china-men-marriage-gender-gap.html 33.59]] ''million'' more men than women in China, with the result that a whole lot of men in a family-oriented culture are unable to marry. This was part of the reason China expanded the limit to two children starting in 2016 and is reportedly even considering ending family restrictions altogether.

* Almost none of the characters in the ''[[Franchise/DCExtendedUniverse DC Films]]'' franchise have siblings. ComicBook/WonderWoman had a brother in her [[Film/WonderWoman2017 first film]] but she kills him at the end. ComicBook/{{Aquaman}} has a half brother but he didn't find out about his existence until his [[Film/Aquaman2018 own first film]]. ComicBook/{{Huntress}} from ''Film/BirdsOfPrey'' had a brother but he died when she was a kid.

* Ron, Hagrid, Sirius, and Dumbledore are the only major characters in the ''Film/HarryPotter'' films who have siblings. Some of them have siblings in the books who are AdaptedOut. However, this averted in the ''Film/FantasticBeasts '' prequel series where almost everyone does. The only main character who is not confirmed as having them is BigBad Gellert Grindelwald who is also not confirmed as being an only child either.

* [[ComicBook/TheMightyThor Thor]], ComicBook/DoctorStrange [[note]] His sister Donna was in a few scenes that got [[DeletedRole cut out of the final film]] [[/note]], and ComicBook/BlackPanther are the only main heroes in the Franchise/MarvelCinematicUniverse who have siblings.

*** Dudley is a fairly extreme example of Only Child Syndrome since his parents [[SpoiledBrat spoil him rotten]]. It's never said why Dudley is an only child, but it may be that the parents felt that having more than one child was unseemly, or it could be them further spoiling Dudley by keeping him as the sole center of their attention.
*** Harry's father James was also an only child, but in his case, his parents Fleamont and Euphemia struggled for many years with infertility and only had James in the twilight of their lives. This led to James becoming a SpoiledBrat due to his parents' overindulgence and his own brilliance and talent.
** Hermione Granger was supposed to have a muggle younger sister, but she got cut from the series when she had nothing to do, leaving Hermione an only child.

** Harry’s godson Teddy is an orphaned only child like him but it’s clear that Harry’s three kids see him as their old brother.

** The Weasleys are an aversion with [[MassiveNumberedSiblings seven children]], as is their mother, who has two (deceased) brothers. Mr. Weasley also been confirmed to have two brothers, one of whom briefly appears without being named in the last book when he thinks Harry in disguise is his son. The Black family are also reasonably filled out, with Sirius having a brother and Narcissa, Bellatrix and Andromeda being sisters.

* Ron, Hagrid, Sirius, and Dumbledore are the only major characters in the ''Film/HarryPotter'' films who have siblings. Some of them have siblings in the books who are AdaptedOut. However, this averted in the ''Film/FantasticBeasts '' prequel series where the only major character who doesn't (or rather isn’t confirmed either way) is the BigBad Grindelwald. Although, Credence had adopted sisters and is told he has biological siblings but it came from an unreliable source and remains to be seen if it's true.

** ''ComicBook/YoungAvengers'': [[ComicBook/KateBishop Kate]] has an older sister, and it's implied that Eli comes from a large family. Billy and Tommy are twin brothers...via reincarnation (it's complicated). Billy mentioned he had two little brothers in the first arc, but over a decade later they've failed to appear in any capacity whatsoever. Teddy is an only child, which isn't too surprising given his parents were on opposite sides of an interstellar war. Same goes for Cassie, as her parents have split up and her father was [[DeathIsCheap dead for a while.]]

* In ''Series/{{Degrassi}}'', the vast majority of the characters that have appeared over the years are only children: Snake (older brother), Liberty (younger brother), Craig (half-sister), and Holly J (older sister) are some of the few exceptions.

** Most Pretty Cures are only children. The only Cures who have siblings are the five mentioned above, [[spoiler:[[Anime/FutariWaPrettyCure Hikari]]]], [[Anime/FutariWaPrettyCureSplashStar Mai]], [[Anime/YesPrettyCure5 Rin, Komachi]], [[Anime/FreshPrettyCure Miki]], [[spoiler:[[Anime/HeartcatchPrettyCure the whole Heartcatch Team]]]], [[Anime/SuitePrettyCure Kanade]], [[Anime/SmilePrettyCure Akane, Nao, Reika]], [[Anime/DokiDokiPrecure Alice]], [[spoiler:[[Anime/DokiDokiPrettyCure Aguri]]]], [[Anime/HappinessChargePrettyCure Yuko, Iona]], [[Anime/GoPrincessPrettyCure Towa, Minami]], [[Anime/HugttoPrettyCure Emiru]], [[Anime/StarTwinklePrettyCure Lala, Elena]], [[spoiler:[[Anime/HealinGoodPrettyCure Chiyu]]]], and [[Anime/HealinGoodPrettyCure Hinata]].
** This means the remaining Cures who don't have siblings are (besides the mentioned lead Cures) [[spoiler:[[Anime/FutariWaPrettyCure Honoka]]]], [[Anime/YesPrettyCure5 Urara, Karen, Kurumi]], [[Anime/FreshPrettyCure Inori]], [[spoiler:[[Anime/HeartcatchPrettyCure nobody of the Heartcatch Team]]]], [[Anime/SuitePrettyCure Ellen, Ako]], [[Anime/SmilePrettyCure Yayoi]], [[Anime/DokiDokiPrecure Rikka, Makoto]], [[Anime/StarTwinklePrettyCure Madoka, Yuni]], [[Anime/GoPrincessPrettyCure Kirara]], [[Anime/HugttoPrettyCure Saaya, Ruru, Homare]], and [[Anime/HappinessChargePrettyCure Hime]]. [[Anime/YesPrettyCure5 Urara]] and [[Anime/SmilePrettyCure Yayoi]] are {{Justified| Trope}} due to having a dead [[MissingMom mother]] and [[DisappearedDad father]] respectively before their parents could conceive a second child. [[Anime/HugttoPrettyCure Ruru]] is justified since she's a robot.

* ''WesternAnimation/DannyPhantom:'' Danny and Jazz are siblings, and if you wanna stretch it, he treats [[OppositeSexClone Dani]] like [[BigBrotherInstinct a little sister]]. However, ''every other secondary character''--[[LoveInterest Sam]], [[ExtravertedNerd Tucker]], [[DatingCatwoman Valerie]], [[JerkJock Flash]], [[AlphaBitch Paulina]], etc.--seems to be an only child.

* {{Averted}} in ''WesternAnimation/TotalDrama''--taking both the show and [[AllThereInTheManual supplementary materials]] into account, only three characters ([[GirlyGirl Zoey]], [[ExtravertedNerd Cody]] and [[{{Geek}} Beth]]) are confirmed to be only children, but about half of the original cast are mentioned to have siblings.

* Except for WesternAnimation/{{Cinderella}} (who has two stepsisters), [[WesternAnimation/TheLittleMermaid Ariel]] (who's the youngest of seven daughters) and [[WesternAnimation/{{Brave}} Merida]] (who's the oldest and only daughter of four kids), all the Franchise/{{Disney Princess}}es are only children -- although you could consider Cinderella an only child in a strictly biological sense (since she's the only child her dad had through his first wife and he didn't have any more biological children after he and Lady Tremaine got married). And for Rapunzel, her status as an only child is [[JustifiedTrope justified]] in that her biological mother's pregnancy almost killed them both--it also very well could've rendered Queen Arianna (Rapunzel's biological mother) unable to have more children through biological means.

* Most lead Pretty Cures from the [[Anime/PrettyCure franchise]] are only children, with the exception of [[Anime/FutariWaPrettyCure Nagisa]], [[Anime/GoPrincessPrettyCure Haruka]], [[Anime/HugttoPrettyCure Hana]], and [[Anime/FutariWaPrettyCureSplashStar Saki]]. However, [[spoiler:[[Anime/HeartcatchPrettyCure Tsubomi]] gets a newborn sister in the final episode]] and [[Anime/FreshPrettyCure Love and Setsuna]] become adopted sisters after the first half of the season. [[Anime/SuitePrettyCure Hibiki]] is actually the only lead Cure who suffers from being an only child while [[Anime/SmilePrettyCure Miyuki]], [[Anime/DokiDokiPrecure Mana]], and [[Anime/HappinessChargePrettyCure Megumi]] don't seem to care.

* In ''WesternAnimation/PhineasAndFerb,'' the title characters' three main friends ([[TheBigGuy Buford]], [[BollywoodNerd Baljeet]] and [[TheChick Isabella]]) are all only children, as is [[MadScientistsBeautifulDaughter Vanessa]]. [[AsianAirhead Stacy]] and [[ScoutOut Ginger]] are [[ConnectedAllAlong revealed to be sisters]] once, but otherwise it doesn't come up, while WordOfGod say that [[OutOfFocus Jenny and Django]] are siblings. Interestingly, all of the major adult characters (Linda, Lawrence, and Doofenshmirtz]] have siblings. [[AnimalSuperhero Perry]]'s status is unknown.

* {{Averted}} in ''WesternAnimation/TotalDrama''--taking both the show and [[AllThereInTheManual supplementary materials]] into account, only three characters ([[TheChick Zoey]], [[ExtravertedNerd Cody]] and [[{{Geek}} Beth]]) are confirmed to be only children, but about half of the original cast are mentioned to have siblings.

* ComicBook/{{Thor}}, ComicBook/DoctorStrange [[note]] His sister Donna was in a few scenes that got [[DeletedRole cut out of the final film]] [[/note]], and ComicBook/BlackPanther are the only main heroes in the Franchise/MarvelCinematicUniverse who have siblings.

** Bruce Banner (Comicbook/IncredibleHulk) is an only child, as is his cousin Jennifer Walters (Comicbook/SheHulk), his wife Betty Ross (Red She-Hulk), and his father-in-law Thunderbolt Ross (ComicBook/RedHulk).

* Averted for [[TheNarrator Saleem]]'s family in ''Literature/MidnightsChildren'', but played straight almost everywhere else. (And even in his case, his grandparents were both only children.) Parents tend to be pretty rare too. This was likely a necessity to keep the LoadsAndLoadsOfCharacters under control; if Saleem's father's family was as complex as his mother's, the book would probably have to be twice as long.

* In ''Series/{{Degrassi}}'', the vast majority of the LoadsAndLoadsOfCharacters that have appeared over the years are only children: Snake (older brother), Liberty (younger brother), Craig (half-sister), and Holly J (older sister) are some of the few exceptions.

* ''WesternAnimation/TheAmazingWorldOfGumball'': The main character's family has three children, but of his approximately twenty classmates, only Penny, Tobias[[note]]His sister, Rachel, [[ChuckCunninghamSyndrome ceased appearing]] even in scenes of his family after season one.[[/note]], and Idaho are known to have any siblings while many of the rest are shown to be only children. Colin and Felix are very similar but not confirmed to be brothers. Among the rest of the school and Elmore's [[LoadsAndLoadsOfCharacters many citizens]], the only ones with known siblings are Margaret, Louie, Hot Dog Guy, and a few very minor characters, while Richard, Nicole, and Rocky are only children.

* In ''WesternAnimation/TeenTitans'', with the exception of Starfire (who has [[CainAndAbel an older sister]] and, [[ComicBook/TeenTitansGo in the tie-in comic]], a younger brother), all of the main Titans are only children.[[note]]The comics would eventually state that Raven has many half-siblings through her demonic father, but that became canon after the show ended. Robin traditionally has several "Bat-siblings," but presumably they won't come until he [[LegacyCharacter stops being Robin]].[[/note]]

* ''WesternAnimation/CodeLyoko'', aside from Yumi ([[AnnoyingYoungerSibling one younger brother]]) and Odd ([[MassiveNumberedSiblings five]] [[OutnumberedSibling older sisters]]), most of the children in Kadic are shown to be only children.

World Of Only Children

People procreate. [[MassiveNumberedSiblings Some do it a lot]]. [[MyBiologicalClockIsTicking Some really want to do it before time runs out]]. [[NotWantingKidsIsWeird Some don't want to do it at all]].

Most examples of ParentalAbandonment in a WorldOfNoGrandparents also feature Only Child Syndrome. Oh, the {{Wangst}}.

Expect some people with Only Child Syndrome to have a few subtleties. Such as, for example, most people who can point out Only Child Syndrome in RealLife can say an only child is often used to never having to compete with anyone else for parental attention, or feeling like they're the only person against the world. Or even a subtle disrespect or having never truly learned to live or communicate (in the worst cases) with others their age. This is in spite of the fact that it has been repeatedly shown in scientific studies that there is not a measurable difference in the personalities of only children as compared to siblings (at least not most of the time - there're a lot of perfectionists in the only child world). Sometimes this also happens with MiddleChildSyndrome, too. Only children also tend to mature faster.

Contrast MiddleChildSyndrome, MassiveNumberedSiblings. May result in SiblingsWanted.