History PlayingWith / OnlyChildSyndrome

** Alice doesn't have any sibling, but she has a ''cousin'', who happen to be the only child just like her, so they start visiting each other more frequently to learn about socialization with other children.

* '''Deconstructed:''' Alice's grandparents are firm believers of this trope, so they unstoppably beg Alice's parents to have more kids to avoid making Alice becomes their only child, despite her parents don't want to and/or unable to do so, causing lots of internal conflicts within family.

* '''Double Subverted''': Bob isn't actually her brother, he is just her friend who is treated LikeBrotherAndSister.

* '''Subverted''': ???
* '''Double Subverted''': ???

* '''Deconstructed:''' Alice's grandparents are firm believers of this trope, so they unstoppably beg Alice's parents to have more kids to avoid making Alice becomes their only child, despite her parents don't want to and/or unable to have more children, causing lots of internal conflicts within family.

* '''Straight''': Alice is independent due to her upbringing as an only child. However, she often feels lonely as a result.
* '''Exaggerated''': None of the characters have siblings.
* '''Downplayed''': ???
* '''Justified''': ???
* '''Inverted''': ???

* '''Zig-Zagged''': Almost all of the main characters have siblings.
* '''Averted''': No personality traits are ascribed to Alice being an only child. She acts like the characters with siblings.

* '''Exaggerated''': ???

* '''Zig-Zagged''': ???

* '''Parodied''': ???

* '''Averted''': ???
* '''Enforced''': ???
* '''Lampshaded''': ???
* '''Invoked''': ???

* '''Defied''': ???

'''Basic Trope''': Most characters in a work are only children, unless the plot requires siblings.
* '''Straight''': The majority of the main characters are only children. One of them has a sister who turned evil, while one of them has a brother who is deceased. These siblings are plot-relevant.
* '''Exaggerated''': The lack of siblings extends to parents and grandparents; there are very few aunts and uncles, as well as very few grandaunts and granduncles. This means that most of the main characters don't have cousins.
* '''Downplayed''': About half to two-thirds of the characters are only children, while the ones with siblings vary in family size, and the siblings vary greatly in plot-relevance.
* '''Justified''':
** The story revolves around a large number of characters whose parents just happened to prefer conceiving only one child.
** The story is set in a time or a place where the population is monitored closely. The people who want families have to stick with only one child.
* '''Inverted''':
** Large families are the norm; almost all of the characters, including those who only appear once, have [[MassiveNumberedSiblings at least eight siblings]]. None of these siblings are relevant to the plot, and the vast majority [[TheGhost only receive mention once]], after Rita mistakes Alice for a boy, and this starts a discussion about the characters' families and a NoodleIncident. Jacob is the only main character who is an exception, and this is because his father fell apart after [[MissingMom his mother died]].
** Most or all of the characters have siblings, but [[ConvenientlyAnOrphan apparently have no other relatives]]. This holds true of all characters, regardless of age.
* '''Subverted''':
** None of the main characters' siblings are mentioned at first, but they start appearing in later episodes. If they are older than the main characters or if the parents are divorced, it is likely that the siblings in question were unseen because they live in another city.
** At first it looks like everyone is an only child, but then in one episode they talk about their families, and several characters are mentioned as having siblings. [[TheGhost They're just unseen.]]
* '''Double Subverted''':
** The pregnancies are forcibly aborted due to Tropistan's one-child policy, except two: [[ConvenientMiscarriage Terrance's mother miscarries]], and Loretta conveniently dies so her baby sister can stay alive. Meanwhile, [[RedShirt Nathan]] dies shortly after his mother's forced abortion.
** The newly-introduced siblings are immediately [[KilledOffForReal killed]] (or [[ChuckCunninghamSyndrome mysteriously vanish]]), possibly due to their [[ShooOutTheNewGuy lack of popularity]].
** [[PosthumousCharacter The siblings in question are deceased, which explains why they are only mentioned.]]
* '''Parodied''':
** Most main characters have siblings at first, but murder them, either [[BecauseDestinySaysSo in accordance with the prophecy]] or because the PopulationControl law ordered them to.
** Sol is WrongGenreSavvy; he assumes that he will be an only child, and when it is revealed that he is not, he freaks out.
--> '''Sol''': What the? I thought I was a fictional character!
* '''Zig Zagged''': There are two main towns in the story. Almost everyone in town #1 is an only child, while most characters who live in town #2 have at least one sibling.
* '''Averted''':
** All the characters in a work have varying numbers of siblings, from more than eight to none, few of whom are important to the plot.
** The characters are all adults, and their families are never shown or mentioned.
* '''Enforced''': "Don't bother creating any irrelevant siblings for the kids. [[LawOfConservationOfDetail We don't want to have too many characters who aren't necessary for the story.]]"
* '''Lampshaded''':
** "No, it's just my parents and I. Come to think of it, does anyone we know have any siblings?"
** "I've never seen someone call themselves a brother or a sister before. I'm not sure I'll live to, either. With the exception of the fair princess and her evil, estranged twin witch."
* '''Invoked''': [[PopulationControl The government enforces a one-child policy due to overpopulation.]]
* '''Exploited''':
** The children enjoy their parents' undivided attention.
** The prophecy states that a descendant of a former hero will become TheChosenOne. As the PopulationControl law has existed for a long time, the heroes each have only one living descendant. Emperor Evulz kills said descendants, thereby [[TheBadGuyWins eliminating the last]] [[TheUnchosenOne apparent]] threat to his EvilPlan.
* '''Defied''':
** The parents break the law and have more children in secret.
** To avoid an aging population, the government of Tropistan repeals the PopulationControl law in favor of a legal age limit; from then on, most people are only allowed to live for 60 years. For the elite, it's 70.
* '''Discussed''': "What? Why should you just assume I was an only child? Even today, you are statistically more likely to have at least one sibling than not to have any. So there."
* '''Conversed''': "Isn't it weird how almost everyone is an only child in these books?" "I know, right? There's no one my family can relate to."
* '''Implied''': All the main characters' parents (and most characters' grandparents) are shown, but never any siblings, and very few uncles or aunts.
* '''Plotted A Good Waste''': The lack of siblings is not just incidental on the part of the writers; it turns out to be an important plot point, and an early sign that Tropistan is not what it seems to be.
* '''Deconstructed''':
** The lower reproduction rate means that parents have one shot at passing on their genes; one tragic death at the wrong time can completely wipe out that branch of the family line. While a prophecy states that a descendant of one of the former heroes will become TheChosenOne, the lines are inadvertently snuffed out before the prophecy can come to pass. Hello, EndOfTheWorldAsWeKnowIt.
** [[ChildMage Ichigo]] is initially forbidden from accompanying Sol because she's her family's only child. Prophecy requiring her presence be darned; they're ''not'' going to lose their baby!
** According to prophecy, only the descendants of the last band of heroes can defeat the emerging evil once and for all. Unfortunately, there aren't too many descendants left; the current generation is made of only children, which TheEmpire is hunting down one by one.
** Fewer births than deaths result in an aging population and a shrinking workforce.
* '''Reconstructed''':
** Prophecies can't be broken that easily: one of the original heroes has a single descendant who has secretly survived by pure chance. They just have to find him.
** Sol reassures Ichigo's parents that she's in good hands, and they reluctantly change their minds.
** [[TheUnchosenOne Yolanda]] stands in for Ichigo, thereby [[ScrewDestiny disproving the prophecy]].
** The "prophecy" turns out to be meaningless, as Sol is [[TheUnchosenOne unrelated to the original heroes]].
** The government is prepared to support an aging population.
** There is a lifespan limit as well as a PopulationControl law.
* '''Played For Laughs''':
** As a RunningGag, Alice asks her parents why she's an only child. They always respond with some variation of "You're ''more'' than enough for us, sweetie." (Alice never seems to pick up on the implication that she is too misbehaved for her folks to risk bringing another, similarly naughty kid into their world.)
** The one-child policy took effect about two years ago and required each family to kill all but one of their children. The government brainwashed the adults but not the surviving children. When the main characters reminisce about their deceased siblings, everyone thinks they're crazy.
* '''Played For Drama''':
** The lack of siblings implies that the human race is in danger of extinction.
** The PopulationControl law is passed in the fourth season of the show, parents are forced to murder all but one their children. ParentalFavoritism is imminent, and [[TheUnfavorite about a third of the cast]] is killed off as a result.
* '''Untwisted''': At first, the characters do not know each other's families, and each assumes that some of the others have siblings. It is [[TheReveal eventually revealed]] (possibly [[AllThereInTheManual only in a supplemental book]]) that none of them do.

Back to OnlyChildSyndrome, and no, you don't have any siblings! There's only one [[TheChosenOne Chosen One]], after all.

** The story is set in a time or a place where the population is monitored closely. The people who want families have to stick with only one child and avoid conceiving another.

* '''Downplayed''': About half to two-thirds of the characters are only children, while the ones who aren't only children have siblings who vary greatly in plot-relevance.

** The story revolves around a large number of characters who just happened to prefer sticking with only one child.

* '''Exaggerated''': The lack of siblings extends to parents and grandparents; there are very few aunts and uncles, as well as very few grandaunts and granduncles. This also means most of the main characters don't have cousins.

* '''Straight''': The majority of the main characters are only children. One of them has a sister who turned evil, while the other has a brother who is deceased. These siblings are plot-relevant.

'''Basic Trope''': Very few characters in a work have siblings, unless the plot requires them to. Has various implications and effects on the setting in general.
* '''Straight''': Out of all of [[TheHero Sol]]'s companions, the only ones with siblings are [[FailureKnight Ernst]] (with his deceased sister [[TooGoodForThisSinfulEarth Marie]]) and Princess Velvet (whose brother is the EvilPrince [[ThemeNaming Satin]]).
* '''Exaggerated''': This lack of siblings extends to the higher generations; there are very few uncles or aunts, resulting in even fewer cousins or other extended family situations.
* '''Downplayed''':
** About half to two-thirds of the characters are only children, while the characters who do have siblings have varying numbers of them. [[FarmBoy Ben]] has the largest family, with seven siblings.
** Only children represent a realistic minority, but most characters have only one plot-relevant sibling or half-sibling. Ida is the sole exception, with two older sisters who are rarely shown. Everyone says that Ida has a large family, implying that she is the ''only'' person they know with more than one sibling.
** The main characters are only children, but most minor characters are not.

** They live in a CrapsackWorld where [[PopulationControl the population is closely monitored and most families can only have one child]]. Couples face severe punishments if caught breaking the law, and the higher class may or may not be exempt.
** If the characters are orphans as well as only children, it could be [[AfterTheEnd a post-apocalyptic setting]] where the vast majority of the global population has been wiped out. If you're lucky enough to have survived, it's '''very''' unlikely that anyone else in your family would have too. And because of government brainwashing, no one has any memories of their deceased relatives.
** Most of Sol's friends once had siblings, but when the PopulationControl law was passed, each couple was only allowed to keep one child.

** Many of the characters' parents conceive after it is established that they only have one child each.

** The unseen siblings are {{imaginary|Friend}}.