[[quoteright:293:[[WesternAnimation/OswaldTheLuckyRabbit http://static.tvtropes.org/pmwiki/pub/images/oswald_meets_mickey_3854.jpg]] ]]
[-[[caption-width-right:293:They haven't seen each other in ''80 years''.]]-]

Our hero or heroine meets someone who they seem to share a number of traits with. The story progresses, and they find themselves working together, at cross-purposes, or [[SurpriseIncest drawing together romantically]].

And then -- TheReveal. The reason our hero has found that other person [[UncannyValley uncannily]] familiar or compellingly attractive is that the new person is a Long Lost Relative they may never have known they had, or had believed gone forever. Variations include [[SeparatedAtBirth blood siblings]], [[LukeIAmYourFather parents]], [[LukeYouAreMyFather children]], aunts, [[LongLostUncleAesop uncles]], cousins once removed, and so forth. This trope is an integral part of the plot in stories where EveryoneIsRelated.

Often this is hinted before it happens -- thanks to SuperPowerfulGenetics members of the same family usually share a number of trademark traits and habits that you can easily spot them by.

Once reunited, the relatives may form a BrotherSisterTeam or join up with the rest of their BadassFamily, since blood is ThickerThanWater.

See FamilyTwistsIndex for more subtropes.

Subtrope of ConnectedAllAlong.

Fair warning. Since this trope involves finding out about long lost relatives -- '''it's rife with spoilers!'''



[[folder:Anime and Manga]]
* ''Manga/SketDance'' dropped a shocking yet somehow logical bombshell when it was revealed that [[spoiler: Bossun and Tsubaki are twins [[TearJerker tragically separated at birth]]]]. Before TheReveal, several characters commented on the similarities between the two. Creepily, because of their constant bickering (read as BelligerentSexualTension) and amusing degree of being similar-yet-opposite, they had a whole contingent of shippers. [[{{Squick}} Not all of them gave up]] when [[SurpriseIncest the truth came out.]]
* A subversion in ''Anime/SpeedRacer''. Racer X knows he's the long lost brother, but no one else does. This is also true in TheMovie, wherein they made a plausible explanation for it because movie Speed wasn't quite as [[strike:stupid]] innocent as his anime counterpart.
* ''Manga/ToLoveRu'' has Kurosaki Mea who claims to be Yami's little sister. Considering they have similar traits (Shapeshifting abilities, assassins, from outer space and being {{exp|y}}ies from Suou and Eve respectively) the claim has a little backup.
* ''LightNovel/{{Slayers}}'' plays with this; WordOfGod confirmed that Lina's first traveling companion, the flaky [[GoldfishPoopGang Naga the Serpent]], is in fact Gracia Ul Naga Seyruun, the first princess of Seyruun and the long-lost sister of one of Lina's later companions, [[RoyalsWhoActuallyDoSomething Amelia]]. They sort of meet three times in continuity: the ''Slayers Evolution-R'' anime had Naga's soul trapped in a suit of armor and became an ally for the group for five episodes, [[NonSerialMovie ''Slayers Premium'']] had Amelia be blasted away before Naga appeared, and the radio drama following the movie had them briefly meet, but Naga simply told Amelia (who didn't recognize her) that she was a friend of Lina's.
* In ''Anime/DinoBreaker[=/=]DICE'', Jet Seigel's brother Zack carbon-copies Racer X pefectly - he fakes his own death, then returns under the guise of Phantom Knight, with only his driving skills clueing Jet (and the audience) in on who he is.
* ''Anime/DragonballZ'':
** ''Dragon Ball Z'' kicks off with the dual revelations that Goku A) is an alien and B) has a much stronger evil older brother.
** More than a decade later, the new ''Anime/DragonballZ'' special gives Vegeta a brother as well. His brother, however, is younger and much weaker, and apparently Vegeta knew of his existence already.
* In ''Manga/FullmetalAlchemist'', it turns out that the BigBad is kind of Ed and Al's ''elder brother'', since he recognized their father as his father, back before he pulled FromNobodyToNightmare, and turned Hohenheim into a monster, too. Complicated by the fact that this 'son' was also kind of his [[EvilMentor mentor]], giving him [[MadeASlave a name instead of a number]] and teaching him to read.
** This relationship means that the homunculi [[FridgeBrilliance are all technically Ed's nieces and nephews]]. But no one makes anything of this within the series.
*** Even when Ed and Al first meet Father, he fixes them up since they're his precious human sacrifices and is fascinated to discover that they're Van Hohenheim's sons and Hohenheim is still alive after all these years, but doesn't therefore think of them in even vaguely familial terms. He seems to restrict those completely to his children; he also doesn't address Hohenheim as his father. Ed and Al return this lack of regard, though since they don't view the flashbacks they may never actually see it put in these terms.
*** Genetically, since Hohenheim was his only parent, once he gets a body Father is Hohenheim's EvilTwin, making him also arguably the brothers' uncle. When he crosses the BishounenLine during the finale, he gets described as '[[GenerationXerox the one who looks like Fullmetal without the automail]]', although he's actually prettier and has somewhat different hair.
*** The relationship between the brothers and the homonculi was referenced at one point near the end when [[spoiler:Pride, his philosophers stone exhausted and body crumbling, attempted to [[GrandTheftMe take Ed's body]] as the reason it was possible was due to that relationship. They're a very creepy family]].
*** Played for laughs in the [[{{Omake}} 4Koma Theater]] gags--Ed reveals to Al that the two of them aren't really two brothers...
-->'''Al:''' So you mean, this blood seal isn't even real!? And I'm ''not'' your younger brother!?\\
'''Ed:''' No, that is a genuine blood seal and you're definitely my younger brother...but your helmet is actually [[spoiler:our younger ''sister'']].\\
'''Al's Helmet:''' [[spoiler:HI BIG BROTHER AL!]]\\
** In [[Anime/FullmetalAlchemist the 2003 anime version]], this is not the case, though during the climatic final battle, [[spoiler:it's revealed that the homunculus Envy is the resurrection-attempt of the son of Dante and Hohenheim, making him sort of Ed and Al's half-brother (as much as Sloth is their mother), depending on how much was retained in the bringing-back-to-life process. Exactly why he looks like Hohenheim's current body, given that Hohenheim is a {{Body Surf}}er, despite being centuries old is anyone's guess]].
* ''Manga/MahouSenseiNegima'': If the source is reliable, it has been confirmed that [[spoiler: Asuna and Negi have a common ancestor in the Lifemaker]].
* Char Aznable and Sayla Mass from ''Anime/MobileSuitGundam'' are brother and sister; though they've been separated for years, they instantly recognize each other when they accidentally cross paths in the second episode. Thus, "Long Lost Little Sister" is often considered one of the defining traits of a CharClone, as seen with [[Anime/MobileSuitGundamWing Zechs Merquise]].
* In ''Anime/TokyoGodfathers'': first Hana and her "mother" (though she's not a blood relation), then [[spoiler: Gin and his daughter]].
* In ''Manga/MyBrideIsAMermaid'', it's revealed that [[spoiler: Masa is Akeno's older brother]].
* In ''Anime/ChancePopSession'', [[spoiler: Akari, Yuki and Nozomi all meet at Kisaragi's music school, not only becoming friends, but harmonizing together well enough to become a successful pop trio, only to learn they are all long-lost sisters, and that the woman who trained them is their mother!]]
* ''Manga/FairyTail'':
** During the [[AlternateUniverse Edolas Arc]] [[spoiler: Happy]] unknowingly runs into his parents while [[spoiler:escaping from the Exceed]].
** Later on, it turns out [[spoiler:Natsu]] is [[spoiler:Zeref's]] younger brother, or rather his ''resurrected'' younger brother.
* ''Manga/RaveMaster'' has main villain Lucia recruiting a number of demons and high profile criminals to beef up his army. Among the new recruits are, unbeknownst to him, his step-brother and grandfather. The grandfather elects not to mention this. Whether or not Deep Snow ever approaches Lucia about their semi-siblinghood is both unknown and unlikely.
* In ''Anime/FutureGPXCyberFormula'', [[spoiler:Osamu is Asuka's older brother]], who ran away from home 5 years before the original series takes place to be a racer in England, and he uses a disguise to protect the team that she's in.
* In ''Anime/NadiaTheSecretOfBlueWater'', it's revealed that Emperor Neo is [[spoiler: Nadia's older brother, Venusis, brought back to life as a cyborg]].
* In ''LightNovel/SaiunkokuMonogatari'', it is revealed that Shi Seiran, the retainer (but practically an adoptive brother) of the protagonist Shuurei's family, is [[spoiler: the exiled prince Seien, the much admired and missed second eldest brother of Emperor Ryuuki]].
* In ''Manga/{{Naruto}}'', we have Tsunade and Naruto. Hundreds of chapters after their initial meeting, it is eventually revealed that Naruto is connected by blood with Tsunade. Tsunade is one of the only two last living blood relatives Naruto has. (The other is [[spoiler:Karin]])
* In ''Anime/StreetFighterAlphaTheAnimation'' Ryu meets a boy named Shun who says he's his younger brother.
* In ''Anime/KillLaKill'', it's revealed later on that [[spoiler:[[TheHero Ryuko Matoi]] is [[TheRival Satsuki Kiryuin]]'s]] younger sister, who was used in experiments with [[spoiler:Life Fibers]] as an infant and tossed away when her mother [[spoiler:Ragyo]] believed her to be dead.
* [[spoiler:Marnie]] from ''Anime/WhenMarnieWasThere'' is Anna's [[spoiler:grandmother]]. In a twist on the norm, [[spoiler:Marnie is the [[DeadAllAlong already deceased]] grandmother, who died when Anna was very young, as a ghost child.]] Anna doesn't recognize this until the climax of the film, and it's implied [[spoiler:Marnie]] didn't know either.
* In ''Manga/TokyoGhoul'', Renji Yomo turns out to be the maternal uncle of [[CainAndAbel Touka and Ayato]] Kirishima. The siblings were still toddlers when he parted ways with their newly-widowed father, and he didn't see them again until they were teenagers. He's avoided telling them who he really is, partially out of guilt for how he feels his actions contributed to their father's eventual death.
* ''Manga/{{Bleach}}'': Ichigo is eventually revealed to be the cousin of Kaien, Kuukaku and Ganju through his father (their uncle), explaining why Ichigo and Kaien look so alike. Ichigo is also eventually revealed to be related to Uryuu, as his mother was the cousin of Uryuu's father.
* ''Anime/SailorMoon'': [=ChibiUsa=]/Rini arrives and stays with the Tsukinos pretending to be a distant cousin. Everyone constantly compares her and Usagi/Serena. From their hair styles, their childish behavior, their love for Mamoru/Darien. It's eventually revealed that she's their daughter from the future and Really700YearsOld
* In ''Manga/Brave10'', although it takes a lot to jog her memory given how greatly he's changed over the years, it turns out Seikai really is Isanami's adoptive elder brother.
* ''Manga/AttackOnTitan'' has several of these:
** A Justified case with Eren and Zeke Yeager, half-brothers that only learn about each other after crossing paths on opposing sides. After escaping execution, Grisha started over and never told Eren about his original family.
** Krista Lenz/Historia Reiss and her father, Rod Reiss. It was almost a decade before she met her father for the first time.
** Mikasa and Levi learn that they are distant relatives, both members of the near-extinct Ackerman Clan. Kenny also eventually reveals that he was Levi's maternal uncle, and that was the reason for taking him in as a child.
* An early chapter in ''Manga/SuperiorCross'' has Angelica meeting her paternal grandfather for the first time, figuring out his identity when she sees a painting of his wife [[IdenticalGrandson that looks near-identical to her]].

[[folder:Comic Books]]
* Baron Helmut Zemo, leader of the Masters of Evil, once took the identity of Citizen V as part of the Masters' plot to pretend to be a team of heroes called the ''Comicbook/{{Thunderbolts}}''. As Citizen V Helmut claimed that he was the grandson of the golden age Citizen, when in fact Helmut's father Heinrich had killed the golden age Citizen V. Helmut was certain the original Citizen V had no descendants. A few years later Techno (worst friend ever) plays a prank on Helmut that pays off when Helmut gets decapitated by Scourge. Helmut finds himself in the body of the man who actually is Citizen V's grandson and Helmut has to go through a similar imposture all over again.
* ''ComicBook/{{Deadpool}}''. The title character discovers he has a daughter he didn't know about from earlier events. He tagged along with other heroes on a mission, hired by a woman to avenge her husband's death. Deadpool meets Carmelita, the woman's daughter, and there's an instant attraction. They get locked in a game-room together to be killed later, and Carmelita decides she wants to spend her last min of life "loving", so she and Deadpool get it on. The relationship comes to an end when she sees Deadpool's face for the first time, and runs away in disgust. However, she shows up later, having finally tracked down Deadpool, who hasn't responded to any of her letters about their baby, or child support. She quickly puts the child in Deadpool's arms, and he seems smitten, but quickly pushes them both away, saying the child is too beautiful to be his. After she and the baby are kidnapped, Deadpool goes to save them. Unfortunately, he finds Carmelita's corpse, along with all the others who were killed, and grieves about how it's his fault. His daughter isn't there -her whereabouts unknown, and Deadpool would not meet her again for another 8 years.
* In ''Comicbook/{{Cable}}'', Mr. Tolliver reveals himself as Tyler Dayspring, Cable's son.
* After dying, the Marvel version of [[ComicBook/CaptainMarVell Captain Marvel]] has acquired a few offspring. [[ComicBook/YoungAvengers Hulkling]] was from a fling he had with the Skrull princess Annelle. Mar-Vell's lover Elysius used Mar-Vell's genetic material after his death to impregnate herself with Genis, and then she sped up his aging process. When Genis rebooted the universe, one change in the timeline was that Elysius did the same thing a second time and had a daughter named Phyla.
* In ''ComicBook/NickFury'', Nick had known his brother Jacob Fury since childhood, but as for being the villain Scorpio, well that, no, that was an LMD that was impersonating him, that he impersonated, revealing that he was really Nick's brother all along, and not the impersonator claiming to be Nick's brother all along.
* In ''Comicbook/{{Shazam}},'' [[TheChosenOne Billy Batson]] has a twin sister, Mary, who was HappilyAdopted by a wealthy couple after their parents died. Finding her results in him joining their family and her becoming his DistaffCounterpart, Mary Marvel.
* Cloak from ''ComicBook/CloakAndDagger'' had a twin sister named Anna. We were never given much detail on why she wasn't raised with Cloak and his other siblings and if Cloak even knows he has a twin sister.
* In ''ComicBook/PowerPack'' we are introduced to a man named Mr. Raymond. It is never fully confirmed who he is but it's strongly hinted that he is the Golden Age superhero Toro (who was presumed dead) and the father of Comicbook/{{Nova}} (Frankie Raye) who was a herald of Galactus. In the meantime a past version of Toro has come to the present and Frankie was thought dead, before she returned.
* [[ComicBook/FantasticFour Reed Richard's]] father Nathan supposedly has at least three other kids thanks to his time-traveling adventures. He went to an alternate earth, married a woman named Cassandra and had an unnamed son with her; that son is supposed to be Kang's ancestor. Nathan tells his daughter-in-law Susan that he once fathered a child with a Latverian woman. A horrified Sue jumps to the conclusion that Reed's arch-nemesis is also his half-brother, but it turns out Nathan was referring to Doom's adopted son Kristoff. Huntarra was raised in alternate timeline with her half-nephew Franklin Richards/Psi-Lord; she later tells him she is Nathan's daughter and thus his aunt.
* ComicBook/ImmortalIronFist's father Wendell Rand married a K'un Lun woman named Shakari and had a daughter with her named Miranda. Miranda's mother was killed by the H'ylthri and a distraught Wendell returned to earth, where he eventually married Heather Duncan and shortly thereafter they had Daniel. Miranda would later take on the identity Death Sting.
* Llyra originally passes Llyron off as her son with [[ComicBook/SubMariner Namor]]. This is later found out to be a lie but Llyron's true father turns out to be Namor's half-nephew Leon. Turns out Namor's father Leonard had a son with a human woman named Lawrence [=McKenzie=] who fathered Leon (Black Moray) who fathered Llyron.
* ComicBook/SilverSurfer discovered that his father Jartran Radd fathered an illegitimate child named Fennan Radd after the death of Norrin's mother Elmar. It's unclear if this is actually true as Zenn-La was retconned as being destroyed by the Other and recreated as an illusion by Galactus to comfort the Silver Surfer.
* In ''ComicBook/{{Wolverine}}'', Dog Logan is revealed as Logan's forgotten half-brother. Eventually, the two meet in modern day.
* ''Comicbook/XMen'':
** Charles Xavier has an EvilTwin sister he didn't know about, who says he tried to kill her in the womb.
** Orphan twins Northstar and Aurora did not know they were twins until they were recruited into ComicBook/AlphaFlight. After their parents' death Northstar went to live with distant relatives who adopted him, while Aurora was raised at a strict Catholic all-girls school.
** Polaris is un-retconned and re-revealed to be the daughter of Magneto; thus she is the half-sister of the Comicbook/ScarletWitch and her former X-Factor teammate Comicbook/{{Quicksilver}} (and their dead sister Anya). As of the events of Axis, the Scarlet Witch and Quicksilver may [[RetGone no longer be related]] to Magneto until another retcon.
** Cyclops's father Christopher Summers (Corsair) met Scott in ''Comicbook/UncannyXMen'' #104, and didn't reveal his identity to Scott until ''Uncanny X-Men'' #154.
** Professor X also hid the existence of Comicbook/{{Cyclops}} and Havok's younger brother, Vulcan.
** Since his introduction in the 1960s is full of FridgeLogic (if Cyclops had been visiting Havok all along, what was the point of: A) keeping his existence a secret from all of his friends, and B) not telling Havok that they were mutants?) Alex Summers is usually introduced as Cyclops's long-lost sibling in newer adaptations (''WesternAnimation/XMenEvolution'', for example). In ''some'' continuities, Comicbook/{{Gambit}} is the third Summers brother.
** Comicbook/{{Storm}} has no siblings, but she does have a long-lost branch of her family on her mother's side that was {{Retcon}}ned into existence to help justify her going back to Africa so she could marry the Comicbook/BlackPanther.
** A subversion occurs with other X-Men: Longtime teammates Comicbook/{{Nightcrawler}} and Comicbook/{{Rogue}} are step-brother and sister.
** Played fairly straight with Nightcrawler's half-brother Graydon Creed (the non-mutant son of Comicbook/{{Mystique}} and Comicbook/{{Sabretooth}}). Rogue also has a few "adoptive" relatives on the side of her other mother, Destiny, including young X-Man Blindfold.
* ComicBook/{{Raven}} from ''ComicBook/TeenTitans'' finds out she is not the only living child of the demon Trigon. She discovers her father Trigon mated with six other women giving her the younger half-brothers Greed, Gluttony, Wrath, Lust, Envy and Sloth (Raven represents Pride). Post-Flashpoint Raven has three older half-brothers via Trigon named Belial, Ruskoff and Suge. When Trigon was first introduced it was implied that over the ages he has had hundreds of children but they had been killed by his enemies.
* In the Comicbook/{{New 52}} continuity, Comicbook/GreenArrow discovers that he has a younger Japanese half-sister named Emiko Queen.
* Satana Hellstrom may count, though when her brother Daimon (Son of Satan) Hellstrom finally met her again, she was kinda sorta ''mistaken'' for being on the other side. (And weirdly, even though they hadn't met since being separated as young children, he'd previously had hallucinations about her with her correct current appearance and costume.)
* ComicBook/SpiderGirl (Mayday Parker), last we saw her, still was not aware that Darkdevil is her cousin (son of her father's clone).
* In some continuities, Comicbook/{{Aquaman}} has a long-lost brother in [[spoiler: Orm, aka Ocean Master]].
* In ''Adèle Blanc-Sec: Le Mystère des profondeurs'', Adèle's little sister Mireille, who not only looks like her but dresses very similarly, with the same taste for ugly hats.
* During the "Elegy" story arc of ''Detective Comics'', it's revealed that [[spoiler:ComicBook/{{Batwoman}}'s nemesis Alice is actually her twin sister Beth, who had been kidnapped as a child and believed dead]]. This revelation [[HeroicBSOD is not taken well]].
* In Creator/MarvelComics, Ka-Zar, Lord of the Jungle, is the long lost brother of deadly pirate the Plunderer, a fact initially only known to the Plunderer himself.
* One cartoon Creator/CharlesAddams did for the ''Magazine/TheNewYorker'' shows two identical men, with identical inventions, sitting side by side in a patent attorney's waiting room. The caption: "Separated at birth, the Mallifert twins meet accidentally."
* Dwayne Taylor, the first Night Thrasher of the Comicbook/NewWarriors, finds out that Donyell aka Bandit is his half-brother. What makes this really odd is that there had been a previous story where Dwayne and Donyell's father Daryl had been commanded to marry and mate with one of the Daughters of the Dragon's Breath Cult by Tai, but he refused on the grounds that he was already happily married to Dwayne's mother.
* ''Franchise/WonderWoman'':
** Prior to the Crisis reboot Wonder Woman had a twin sister named "Nubia" who was stolen by Mars, the god of war, after creation.
** In the ComicBook/New52, Wonder Woman has a long-lost twin brother named "Jason".
* After the events of the Comicbook/MarvelNOW relaunch, Comicbook/IronMan learned he secretly had an older brother named Arno Stark.
* During the ''Comicbook/OriginalSin'' tie-in of ''Comicbook/LokiAgentOfAsgard'', [[ComicBook/AngelaMarvelComics Angela]] from the ''Comicbook/{{Spawn}}'' universe is revealed to be the older sister of [[Comicbook/TheMightyThor Thor]] and Loki.
* ''ComicBook/{{Impulse}}'': Bart (who is from the future) discovers that he is half-brother to Captain Boomerang II, on his mother's side.

[[folder:Fan Fiction]]
* More FanFiction than you can shake a rolled-up newspaper at. Long Lost Siblings are always crawling up out of the woodwork.
** More ''Franchise/HarryPotter'' fanfics than you can count feature Harry's long-lost sister, [[MarySue Mary Sue Potter]].
** A lot of ''Animorphs'' fanfics feature Tobias's long lost sibling, usually his sister. It was parodied in one fanfic; Tobias complaining about having to take of so many siblings.
** Used frequently to justify {{Copycat Sue}}s
* Having Mulder's sister turn up is common in ''Series/TheXFiles'' fanfics. One troper read one [[spoiler:in which it turns out Monica Reyes started life as Samantha Mulder]], and is sure that one wasn't unique.
* These were as common as grains of sand in the early days of the ''Franchise/SailorMoon'' fandom. They'd almost universally be either Usagi or Mamoru's long-lost sister, though once in a great while Usagi would have a brother (since apparently she doesn't get enough grief from Shingo) or one of the other senshi would suddenly sprout a sibling or two. What was particularly odd with Usagi's many sisters was how often they were her ''older'' sibling, but were still usually banished (and thus forgotten by everyone until after the canon series) for breaking the "one heir" rule. Because it makes perfect sense to banish the ''firstborn'' for being an extra child.
* Justified example in the ''Manga/DetectiveConan'' fandom. This is a popular fan theory for ''Manga/DetectiveConan'''s lead Kudo Shinichi and his {{foil}} and WorthyOpponent the [[PhantomThief Kaitou Kid]]. (Who had his own very brief manga series before Aoyama started Conan and folded Kid into it.) Generally they're either twins and don't know it, or first or second cousins, but there have been considerable variations.
** This is all based on the fact that they canonically look ridiculously similar, when seen in 'normal' form. Interesting meta-use of OnlySixFaces, since what the manga-ka actually did was use the same basic design for two heroes and then {{lampshade|Hanging}} it--specifically, by showing that Kid, a MasterOfDisguise who usually relies heavily on LatexPerfection, can dress as Shinichi without a mask. Just has to change his hair and body language.
*** Wasn't that just in some of the movies? Those are canon, though.
** The backstories fans produce for these EpilepticTrees can be ''epic''. One nightmare scenario from a world where they had been SeparatedAtBirth had them ''not'' having been SeparatedAtBirth, and instead raised by the Black Organization as evil SingleMindedTwins.
*** A few horrible shippers use this theory for SurpriseIncest {{Squick}}.
* The big reveal in the ''WesternAnimation/RiseOfTheGuardians'' fanfic ''[[https://www.fanfiction.net/s/8751000/1/Guardian-of-Light Guardian of Light:]]'' [[spoiler: Pitch is the biological father of the main character, Helen, who was taken into the future by Bunny on the day of her birth in order to protect her]]. Oh, and [[spoiler: her biological sister is Mother Nature]].
* ''FanFic/{{Hivefled}}''; [[spoiler: Gamzee and Feferi turn out to be siblings SeparatedAtBirth, and Gamzee is hanging around with the ghost of Sollux's centuries-dead half-sister who is also his and Feferi's half-sister on the other side of the family]].
* When Elden meets Mrs. Bones in ''FanFic/AFarGreenCountry'', Elden learns that Mrs. Bones is really Elden's lost sister Beorna.
* In ''Fanfic/{{Chlorine Grown Roses}}'', the main character, Azusa Tachibana, is Makoto's long lost cousin from America.
* The prototypical version of Brittany from ''Franchise/AlvinAndTheChipmunks'' was a oneshot character named Charlene. In fan works she sometimes appears as a long lost sister or cousin to The Chipettes.
* The BigBad of the ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' fic ''FanFic/PrincessTrixieSparkle'' Astel is revealed to be [[spoiler: Celestia and Luna's long lost older sister, that Celestia had been keeping a secret.]]
* [[http://www.fimfiction.net/story/54077/2/a-family-reunited/a-family-reunited This]] My Little Pony fic centers around Rainbow Dash and Trixie being long lost sisters.
** While we're on this subject, it is also somewhat popular to have Trixie revealed to be Twilight's lost sister, due partially to Trixie's cutie mark looking similar to Twilight's father's from a distance.
* ''Fanfic/MGLNCrisis'': After taking a DNA test and doing some investigating, Fate finds out that her biological father was [[spoiler: an aged up clone of]] Clyde Harlaown, meaning that Lindy is her step-mother and Chrono is her half-brother. Of course, Lindy had already been her adoptive mother for over a decade at this point, so it didn't change anything between them.
* In ''Fanfic/ChildOfTheStorm'', this happens a ''lot'' - the central premise is that Thor was incarnated as James Potter, then had his memories of that blocked, because being murdered is detrimental to one's sanity, and the plot is triggered by those memories being triggered. And it's looking more and more like Doctor Strange arranged it as part of his grand plan.
** ''[[Fanfic/ChildOfTheStorm Ghosts of the Past]]'', it's eventually revealed that [[spoiler: Maddie Pryor is ''not'' Jean Grey's clone, as in the comics, but rather Jean's twin sister Rachael, whom Sinister abducted as an infant after faking her death]].
* ''[[http://www.fimfiction.net/story/150864/scootaloos-sunrise-surprise Scootaloo's Sunrise Surprise]]'': After her friends, Rainbow Dash and Twilight learn the truth about Scootaloo's parents (who are a noble family and very much love her), Scootaloo's father privately confesses to Twilight and Rainbow Dash that Scootaloo also has a long-lost older sister, a unicorn who had to live in Canterlot instead of Cloudsdale and lost touch with her family before Scootaloo was born. Twilight subsequently helps Scootaloo and her father (and Rainbow Dash, who tags along) reunite with said sister: [[RelatedInTheAdaptation Sunset Shimmer]].
* ''Fanfic/PokemonResetBloodlines'' took the {{Identical Stranger}}s from the original series and turned them into Ash's half-siblings, making it clear that their physical resemblance is not a coincidence, but a result of sharing the same father. On top of that, there's the implication that there are more siblings out there in the ''hundreds'' spread across all regions in the Pokémon world.

[[folder:Film Animated]]
* One of the ''Franchise/DisneyFairies'' films involves Tinker Bell finding out she had a twin sister she never knew of named Periwinkle that is a frost fairy. [[spoiler: Both get born from the same laugh but Tinker was the one who reached the Pixie Dust Tree in Pixie Hollow while Periwinkle got lost by the wind and reached the Pixie Dust Tree's branch in the Winter Woods.]]

[[folder:Film Live-Action]]
* ''Franchise/StarWars'', natch:
** Luke and Leia are twins, and meet when one (farmboy from a backwater planet) rescues the other (political prisoner on the Death Star) with neither being aware of who they are, though it's implied that they recognized each other on an instinctual level due to their Force-sensitivity.
** Obi Wan Kenobi was mentioned to have a brother, the original idea being that Owen "Luke's uncle" Lars was Obi-Wan's brother, not Anakin's.
** [[ItWasHisSled Of course, we can't forget]] Darth Vader, revealed to be [[LukeIAmYourFather Luke's father]] in ''Film/TheEmpireStrikesBack'', and who in turn learns that [[LukeYouAreMyFather Leia is his daughter]] in ''Film/ReturnOfTheJedi''.
** Luke and Leia are also this to their mother's family back on Naboo, as they were all led to believe that Padme was still pregnant when she died. For a long time Leia had no idea that one of her friends from the Imperial Senate was actually her first cousin.
** [[Film/TheForceAwakens Kylo Ren]] is [[spoiler: Han and Leia's son]], but this is mostly only a secret to the audience. All of the family members in question discuss the relationship openly whenever they meet. Meanwhile Rey ([[WildMassGuessing and the audience]]) is still waiting for the penny to drop on who her family might be.
** Gunn Yage is Cade Skywalker's half-sister in the comics, making this trope InTheBlood.
* ''Film/TheAddamsFamily'' is kind of an inversion. Fester is returned to the family by a con woman who thinks he's ''not'' the real long-lost Fester, brother of Gomez. But he ''is''. Only with TraumaInducedAmnesia.
* [[spoiler: Penny Priddy]] was the unknowing long lost twin sister of [[Film/TheAdventuresOfBuckarooBanzaiAcrossThe8thDimension Buckaroo Banzai's]] wife, [[DisposableWoman Peggy]]. Tragically, the sisters never had the opportunity to meet.
* In ''Film/BrewstersMillions'', Monty Brewster's long-lost half-uncle leaves him $300 million, if he can spend $30 million in thirty days with no help ''and'' no tangible assets to show for it..
* In ''Film/{{Desperado}}'', [[CainAndAbel El Mariachi and Bucho]] are brothers.
* Just like ''Star Wars'', ''Film/HalloweenII1981'' used it as a major plot point. In [[Film/{{Halloween 1978}} the previous movie]], Michael Myers, the homicidal maniac, remained an unknown menace: no face and no real motivation behind his crimes. But as his very first victim happened to be his elder sister, when an explanation was needed about the murders, the former storyline changed "totally": Laurie Strode, the final girl, was not just any stalked babysitter. She is Myers' younger sister, born only two years before he stabbed the other one, and who was adopted after her parents' death in a car crash. Since then, movie after movie, it's quite clear that Myers only dreams of one thing: murdering each and every member of his family (and their friends, as there wouldn't be enough blood if he didn't slice and dice a dozen idiotic teenagers every year).
%%* Will Turner's father Bill in ''Film/PiratesOfTheCaribbeanDeadMansChest''.
%%* Raymond from ''Film/RainMan''.
* In the Robin Hood retelling, ''Film/RobinHoodPrinceOfThieves,'' [[spoiler:Will Scarlett ends up being Robin's half brother, related through their father]].
* Cameron Vale and Darryl Revok in ''Film/{{Scanners}}''. Revok is trying to get Cameron to [[WeCanRuleTogether join him]], but when the reunion comes, [[spoiler: they kill each other with PsychicPowers]]. [[LeftHanging Probably.]]
* In ''Film/{{Scaramouche}}'', the villain is revealed to be the hero's half-brother.
* In the ''Franchise/{{Scream}}'' trilogy, Sydney Prescott's mother Maureen is killed by the original Ghostface killer before the events of the first movie. The Ghostface killer in the 3rd movie turns out to be Roman Bridger the son Maureen gave up for adoption. He was conceived when his mother Maureen was gang raped at a party and his father is presumed to be John Milton who was the producer of the Stab movies which were based on Gale Weather's book about the original Ghostface killings.
* In ''Film/{{Soapdish}}'', soap opera costars Lori and Jeffery nearly kiss before Celeste breaks them up to reveal that Lori is his daughter. Ew.
* Spock's touchy-feely half-brother Sybok in ''Film/StarTrekVTheFinalFrontier''. As well as Kirk's son David from ''Film/StarTrekIITheWrathOfKhan''.
* Creator/ArnoldSchwarzenegger and Creator/DannyDeVito portray the titular long lost brothers in the comedy film ''Film/{{Twins}}''. In an unusual departure from the twin trope, they are [[CaptainObvious fraternal twins]].
* There have been a few variations on this with twins who were SeparatedAtBirth, such as ''Film/TheParentTrap'' and ''Film/{{Twitches}}''.
* ''Film/XMenDaysOfFuturePast'': Screenwriter [[WordOfGod Simon Kinberg]] confirms that [[http://www.comicbookmovie.com/fansites/JoshWildingNewsAndReviews/news/?a=108298 Magneto is Quicksilver's father,]] so the trope is played with in this case because although Erik suspects that Peter is his son after the teen mentions that his mother once knew a guy who could control metal, the older mutant doesn't try to seek out the truth or inform anyone else about the potential blood relation.
* ''Film/ZorroTheGayBlade'' has a SeparatedAtBirth sitch with Bunny Wigglesworth. Bunny knows they're brothers. Diego did know he had a brother. But he hadn't seen his brother in years since Bunny had been in the Navy. Also, Bunny's birth name was Ramone and Diego wasn't aware that he had changed his name.
* ''Film/AustinPowers in Goldmember'' reveals that Austin's recurring nemesis Doctor Evil is actually his long lost twin brother Douglas "Dougie" Powers. They were separated as babies in a car crash and their father Nigel gave up on Dougie when he saw him being picked up by a pair of passing Belgians which ''immediately'' turned Dougie evil. Belgium is apparently a wellspring of evil in this setting because they share a border with the Dutch. Austin and Douglas are both shocked when Nigel reveals the truth, though Douglas only takes a second or two to immediately embrace his lost family.

* Feirefis, Parzival's Moorish long-lost half-brother and ancestor of Prester John is only one of several long-lost relatives in Wolfram von Eschenbach's epic poem ''Parzival'' where EveryoneIsRelated.
* The titular character in ''Literature/SirAproposOfNothing'' discovers he has a long lost sister, not quite in time to escape BrotherSisterIncest, but at least to escape marrying her. Unfortunately, he doesn't tell her, which results in her hating him for dumping her so unceremoniously.
* ''Literature/TheDresdenFiles'':
** Harry Dresden discovers fairly early in his adventures that he has a long lost half-brother, [[spoiler: Thomas]].
** In ''Changes'', he discovers that he has a long lost [[spoiler:daughter and grandfather]] as well. Where it gets tricky is that it makes [[spoiler:Ebenezar ''Thomas's'' long-lost grandfather]], something neither of them are aware of (and might not be happy to find out). Harry's pretty careful about who he tells what: as of ''Skin Game'', nearly everyone knows [[spoiler:he has a daughter]], but good luck keeping track of who knows about [[spoiler:Ebenezar and/or Thomas]].
* The Baudelaire siblings encounter two of a set of triplets in ''Literature/ASeriesOfUnfortunateEvents'' -- the third triplet is a LongLostSibling who eventually reunites with his brother and sister.
* Arthur Spiderwick is the long lost DisappearedDad of ''Literature/TheSpiderwickChronicles''. The same is true for TheMovie.
* In the first book of ''Literature/TheObsidianTrilogy'' by Creator/MercedesLackey and James Mallory, Kellen Tavadon finds that Idalia, the person who nurses him back to health, is his sister (and that their father gave him LaserGuidedAmnesia to avoid bothersome questions from a six year old).
* ''Literature/TheKiteRunner'' reveals that [[spoiler: Hasaan is Amir's half-brother]] in a climactic reveal.
* In ''Literature/{{Havemercy}}'' Thom eventually realizes that [[spoiler:Rook]] is his brother, leading to a lot of protest among fans who ''insist'' that their UST is undeniable (and it really is....)
* Something like this happens in ''The Literature/BlackFleetCrisis'' of the ''Franchise/StarWarsExpandedUniverse''. In one of the two ultimately pointless major plotlines, Luke meets a woman who claims to be close friends with his mother. Apparently a lot of people claim that kind of thing, but he believes this one, since she's Force Sensitive. But she's part of a sect of extremely strict {{Actual Pacifist}}s and she gives him a bunch of [[SecretTestOfCharacter Secret Tests Of Character]] to see if his mother would approve of him, and since Luke readily uses weapons to defend himself and her, he fails all of them. And then it turns out that no, she was lying about knowing his mother and apparently just wanted a chance to moralize on Luke.
* ''Literature/OldKingdom'' series: Turns out Sabriel has a [[spoiler:half-sister]], which is a very good thing considering that neither of her kids is Abhorsen material.
* The ''Literature/MollyMoon'' series is full of these. In the course of four books, [[spoiler:Molly goes from having no family at all to discovering her mom (Lucy), dad (Primo Cell), her evil uncle (Cornelius), twin brother (Micky), and half-siblings through adoption (Sinclair and Sally Cell)]]
* ''Literature/TheMortalInstruments'':
** [[spoiler: Valentine Morgenstern is Clary’s biological father]].\\
[[spoiler:Jace and Clary end up being siblings... though not before they've sort of fallen in love with each other. Oops...]]\\
[[spoiler:Once you get to ''City of Glass'', you find out that Jace and Clary ''aren't'' related, and that Clary's actual brother is Sebastian]].
** Amatis Herondale to [[spoiler:Luke, more or less, although it's more of the fact that they're estranged siblings and Luke's afraid that she'd blame him for her divorce]].
* ''Literature/TheHeroesOfOlympus'':
** In this ''Literature/PercyJacksonAndTheOlympians'' sequel series it is discovered that[[spoiler: Jason is Thalia's little brother. And no, not just because they share the same father. They're actual, full-blooded siblings]].
** Hazel is Nico’s sister and Frank turns out to be a descendent of Poseidon, so Percy and Tyson adopt him as their brother.
** Leo is related to Sammy Valdez, Hazel's boyfriend from back during World War 2—specifically, he is Sammy's great-grandson.
** Heracles & Chrysaor to Jason and Percy. They try to kill each other.
* In ''Literature/EndersShadow'' (the parallel novel to ''Literature/EndersGame'') we find out the backstory of Bean, a super-smart little genetic experiment who was kidnapped as an ''embryo'', escaped captivity as a baby, and made it to the orbital battle school as a small child. He managed to forge a real friendship with exactly one other person in the school, who turns out to be the son of the people whose embryo was stolen, meaning Bean sought out and befriended his long-lost brother.
* Jessie Shimmer finds out she has multiple long lost relatives [[spoiler: her father Ian]] and [[spoiler: her older brother Randall]] in ''[[Literature/{{Spellbent}} Shotgun Sorceress]]''.
* In ''Literature/TheVampireDiaries: Midnight'' it is revealed to Meredith Sulez, by her parents no less, that she has a twin brother who was kidnapped by [[BigBad Klaus]] when she was just a baby. [[spoiler: She also discovers that she is a type of vampire with kitten teeth.]]
* Played to a ridiculous level in the {{Wuxia}} ''[[http://en.wikipedia.org/wiki/Demi-Gods_and_Semi-Devils Demi Gods and Semi Devils]]'' with the protagonist's father, Duan Zhengchun, being a big case of TheCasanova. ''Every single'' {{Love Interest|s}} his son, Duan Yu, meets in his journey turns out to be his half-sisters. [[spoiler: Though this is subverted later on as Duan Yu isn't Zhengchun's son, thus resulting in Duan Yu [[MarryThemAll marrying all of them]].]]
* In the eleventh ''LightNovel/HaruhiSuzumiya'' light novel, [[spoiler: [[BigBad Fujiwara]] claims to be [[{{Moe}} Mikuru's]] younger brother]]. The alleged sibling denies it, but the two of them seem to have some history together, [[spoiler: though the versions of them we see are from different timelines]].
* In Creator/JaneAusten's ''Literature/LoveAndFreindship'', Laura lucks on her grandfather, followed by a positive cascade of discoveries.
* Jerin and Princess Ren in ''Literature/ABrothersPrice'' find out that they are third cousins, sharing great-great-grandmothers. His grandfather was thought to be lost by family, but instead had been abducted and married to his grandmothers. This relation is distant enough that it does not [[KissingCousins hurt the romance]], and in fact the RoyalBlood that Jerin thus possesses means it's possible for them to marry.
* In ''Literature/{{Scaramouche}}'', the villain was the hero's father.
* In ''Literature/TheLostYearsOfMerlin,'' Emrys ([[MeaningfulRename i.e., Merlin]]) first gets a LukeIAmYourFather [[spoiler:from Stangmar]] in the first book, and in the second finds out that [[spoiler:his friend Rhia]] is his sister.
%% ''Literatue/Theatrica''
* In ''The Five Little Peppers and How They Grew'' it turned out that the Pepper children's mother and their rich benefactor's son-in-law were cousins.
* In ''Literature/EmpireOfTheEast'', the Lady Charmian's long-lost younger sister is unknowingly serving her as a handmaiden. Each of them lost their memories of the other as the result of encountering a demon as young girls. [[spoiler:Well, "encountering" might be too mild; their father ''gave them to it'' as his pledge of loyalty- the demon allowed them to live for its own reasons...]]
* The plot of ''Fort Hope'' largely revolves around the protagonist, Greg, trying to get to know his long lost relatives. His love interest also ends up learning about relatives that she never knew she had.
* In ''Literature/DoctorZhivago'', Yuri Zhivago learns that his deadbeat father had an illegitimate son with Princess Stolbunova-Enritsi named Yevgraf. Later on, Yevgraf ends up being an important but enigmatic character, helping Yuri and his loved ones to escape most of the chaos brought on by the Russian Revolution.
* ''Literature/FirstLight'': [[spoiler: Peter and Thea are cousins. Peter's mother left Gracehope years earlier before coming back]].
* In ''[[Literature/TheRedVixenAdventures Shadow of Her Sins]]'' Alinadar, who was enslaved by pirates at the age of six, meets an older brother she didn't remember she had.
* In ''Litereature/FiveKingdoms'': ''Crystal Keepers'', The Hunter that is working for the High Shaper is actually [[spoiler:Hunter Randolph, the older brother of the main protagonist, Cole. He actually got sucked into the Outskirts a couple of years before Cole, which is why Cole has no memory of him. (When somebody gets sucked to the Outskirts from Earth, those closest to them on Earth forget that they ever existed.) Of course, when Hunter tells him this, he believes it to be an elaborate ruse at first, especially since Hunter is working for the enemy. Hunter, however, provides enough evidence to make it very doubtful to both Cole and the readers that he could be anything but Cole's brother and then backs it up with deeds after he verifies that the shady stuff that Cole tells him about the High Shaper that the High Shaper had been hiding from him is true]].
* In the ''Literature/BlackBlade'' series, protagonist Lila Merriweather is the first cousin of [[spoiler:Deah Draconi, the BigBad's WhiteSheep daughter]].
* In ''Literature/DoctorSleep'', [[spoiler:Danny and Lucy]] discover they're half-siblings, sharing their father, whom the younger sibling never met.
* In ''Literature/TheGirlFromTheMiraclesDistrict'', Nikita discovers that [[spoiler:she and Ture]] are twins.

[[folder:Live-Action TV]]
* On ''Series/SixFeetUnder'' George Sibley's illegitimate son Kyle was a bit bitter and sent his father boxes of feces.
* Nichols family patriarch Caleb Nichols has an illegitimate daughter named Lindsay on ''Series/TheOC'' in addition to his 2 other daughters Kirsten and Hailey.
* Tommy Gavin from ''Series/RescueMe'' learns that his father Michael fathered an illegitimate son who has grown up to be Father Liam Murphy a catholic priest. Tommy learns that his half-brother is molesting the teenage boys he is mentoring and puts a stop to it.
* On ''Series/TheGoldenGirls'', Blanche's husband George died of a heart attack before the events of the series. During the series she encounters a man named David who reveals that he is the son of George and was conceived during George's affair with another woman. Blanche does not take the news well.
* Howard from ''Series/TheBigBangTheory'' discovered he had a half-brother, the product of a relationship his father had after he walked out on Howard and his mother.
* A recurring theme on soap operas. One prime example is ''Series/DaysOfOurLives'' villain Stefano who over the course of the show has been revealed as the long lost biological father of Tony, Renee, Megan, Benjy, Lexie, Ej, Chad and the adoptive father of Kristen and Peter. In the end Tony turned out not to be his.
* ''Series/{{Lost}}'':
** When Jack and Kate get off the island they concoct a ruse to protect the island from the outside world and part of this lie includes hiding the fact that Aaron is fellow 815 survivor Claire's baby and so they pass Aaron off as Kate's son. At the funeral for Jack's father Christian he meets Claire's mother Carol who tells him that her daughter was also Christian's daughter and that she was on the flight with Jack and her name was Claire.
** Daniel turns out to be the son of Charles Widmore and Eloise Hawkings. And the half-brother of Desmond's lover Penelope.
*** Locke's biological parents re-enter his life to trick him out of his kidney. Locke's father later destroys Locke's relationship with the love of Locke's life and later still paralyzes Locke when he knocks him out a window.
* ''Series/AsTheWorldTurns''.
** Subversion: A lot of people expected Reid to be revealed as a relative of John Dixon, given their similarities, but the only relative revealed was Reid's uncle, as both his parents were dead.
** [[PlayingWithATrope Played straight]] with Gabriel (Craig's illegitimate son), Liberty (Brad's daughter conceived when he was a teen), Rose (Lily's twin sister). DoubleSubversion with Jade, who only [[CoattailRidingRelative pretended to be Rose's long lost daughter to get money from Lily]] before finding out she actually was.
* On ''Series/TwentyFour'' the nemesis who appears to have orchestrated most of the events of the fifth season is revealed in the sixth to be Jack Bauer's estranged (and never before mentioned) brother Graem who was also being manipulated by their father.
* In ''Series/{{House}}'', a married couple who grew up next door to each other learn that they are in fact half-siblings. Not quite long-lost, but close.
* Something similar happened in ''Series/LawAndOrderSpecialVictimsUnit'', where a teenager found out he'd been dating/sleeping with his (now-murdered) half sister. He was originally a suspect, but Stabler considered him innocent when the revelation actually made him throw up. [[spoiler: His father killed the girl by accident, then the boy's mother murdered the father after she found out that he had been cheating on her all that time.]]
* ''Series/GameOfThrones'': In the sixth season finale it is revealed that [[spoiler:Jon Snow's real parents are Lyanna Stark and Rhaegar Targaryen. This makes Daenerys Jon's aunt, and Maester Aemon his great-great-uncle. His presumed father Ned Stark is actually his uncle, and his presumed Stark half-siblings are actually his first cousins]]. Daenerys' poor mother Queen Rhaella had ''seventeen years'' of miscarriages and still-births between Rhaegar and Viserys and then another eight year gap before conceiving Dany. Rhaella finally gives birth to her only living daughter Daenerys approximately 8 to 9 months after Lyanna Stark gave birth to her son Jon, resulting in Jon being slightly older than Daenerys. Dramatically enough, Maester Aemon and Jon bonded over their families being in trouble (Aemon with his Targaryen family and Jon with his Stark family) and wanting to help them, driven by their love for their families and anguished by their Night's Watch vows — all the while not knowing that they share their own family tie via their Targaryen blood.
* ''Series/PushingDaisies'':
** Ned's DisappearedDad started a new family after abandoning Ned at boarding school, then pulled the DisappearedDad thing again. As a result, the Pie Maker has twin half-brothers. In a bit of a subversion, Ned's always been aware of the twins' existence; he just didn't want anything to do with them until recently.
** And [[spoiler: Ned's own father]] has turned up, making one more Ned-relative who has returned from being long lost.
* ''Series/NipTuck'':
** Perpetual fuck-up Matt has sex with one of his father Christian's patients Emme. After they do the deed Emme reveals that she came to town to meet her father who is Christian. They seriously consider staying together as a couple after they find out.
** Christian eventually meets his biological mother and one of her other 2 children and finds out his mother put him up for adoption because she became pregnant as a teenager when she was raped by a stranger and her parents had been too religious to allow her to have an abortion.
* ''Series/KyleXY'':
** Jessi is not Kyle's sister, but she was born in the same laboratory and was cloned from [[spoiler: Kyle's biological father's lover]]. At least until the ending which made them not be clones without explaining it very well.
** A straighter use of the trope occurs in the [[CutShort not-really-a-finale]]: [[spoiler:Cassidy is Kyle's brother, although born naturally and thus lacking any of Kyle's powers]].
* ''Series/DueSouth'''s Constable Benton Fraser meets his half-sister in the show's penultimate episode.
* Detective William Murdoch of ''Series/MurdochMysteries'' discovers that he has a half-brother in the Season 2 finale.
* ''Series/{{Heroes}}'':
** Two opposing factions played on [[spoiler: Gabriel Grey]]'s mental issues to manipulate him. The vehicle they used to do this? [[SubvertedTrope They lied]], telling him he was a long lost family member.
** A better example lies in Alice, [[spoiler:Angela Petrelli]]'s [[YouDidntAsk never-before-mentioned]] sister.
** Eventually Sylar does have real long lost relative issues. He tracks down Martin Gray the father that abandoned him and discovers that Martin is only his uncle. Sylar's real father Samson Grey killed Sylar's mother and sold their son to his brother Martin and Martin's wife Virginia who was infertile.
* ''Series/{{Monk}}'' discovers he has a long lost brother.
* ''Series/StarTrekDeepSpaceNine'':
** Benjamin Sisko finds out his real mother was inhabited by one of the prophets of the Bajoran wormhole. Benjamin's birth was arranged by the prophets and the entire time Benjamin's father was with Benjamin's mother she was possessed by the prophet. Benjamin's real mother promptly leaves Benjamin's father after the prophet quits possessing her. Benjamin's father later marries another woman with whom he has more children and Ben is raised to believe his step-mother is his real mother.
** Gul Dukat discovers his bastard daughter Tora Ziyal with a Bajoran woman is alive on a Breen prison world. Originally he plans to kill her but later accepts her into his family. Dukat later fathers a child with another Bajoran woman in his pah wraith cult and tries to claim the child is really that of her husbands but was somehow transformed by the pah wraiths as part of their covenant. Kira doesn't buy it.
* ''Series/StarTrekTheNextGeneration'':
** The series pulls this one, with the twist of it being ''the android'' whose mother has shown up. A couple of his brothers have shown up too. One is evil, the other just dumb.
** Worf's long lost brother Kurn also shows up as well as his long lost son Alexander. Picard visits his estranged brother Robert and meets his nephew Rene for the first time. Riker's estranged father visits. Troi finds out she had an older sister who drowned that she never knew existed. Tasha Yar's sister also visits the Enterprise after her death.
* ''Series/KamenRiderKiva'' has Wataru Kurenai learn that [[spoiler:Taiga Nobori, his childhood best friend, is in fact his older half-brother by way of their mother Maya. Neither of them knew this until Maya told Taiga, who then told Wataru]].
* ''Series/KamenRiderDouble'' has [[spoiler:Phillip]] find out that [[spoiler:Wakana]] is his sister. After he's been acting rather close to her, but apparently it was sibling love all along, so it's okay.
* ''Series/{{Charmed}}'':
** This trope is the only thing that saved the show after Creator/ShannenDoherty left and her character, Prue, was KilledOffForReal. In the first episode of the fourth season, Piper and Phoebe find out that the affair their mother had with their Whitelighter ([[ArcWelding that was fortunately established a season and a half earlier]]) led to the birth of their younger half-sister, Paige.
** The sisters impersonate their own long lost cousins in the first few episodes of the eighth season.
* Parodied in ''Series/SabrinaTheTeenageWitch'' in an episode where Sabrina's magic turns her life into a soap opera. A police detective and model bump into each other at a FashionShow.
--> '''Detective:''' Have you ever been to the Grand Canyon?
--> '''Model:''' Only as a child.
--> '''Detective:''' Beverly?
--> '''Model:''' Kenneth!
--> '''Detective:''' My long lost sister!
* ''Series/{{Supernatural}}'':
** In the 4th season episode "Jump the Shark," Sam and Dean meet a young man named Adam, who says John Winchester was his father, making him their half-brother. After spending much of the episode trying to determine if this is true (while also trying to help Adam find out what happened to his missing/ possibly dead mother), they discover that he's lying... [[spoiler: he's really a ghoul who killed and is now mimicking the ''real'' Adam... who ''was'' their brother.]]
** Season 6 introduces Samuel Campbell, the brothers' maternal grandfather, as well as cousins Gwen, Christian, Mark and Johnny Campbell [[spoiler: (the last one dies before his introduction)]].
** In season 8, the brothers encounter Henry Winchester, their paternal grandfather who was believed to have abandoned the family [[spoiler: (He used Men of Letters magic to time jump to the future but was killed before he could return to his own time.)]]
* ''Series/TheVampireDiaries'':
** [[IdenticalGrandson Katherine is Elena's great-great...grandmother.]]
** Alaric, due to his marriage to Isobel is Elena's stepfather.
* In the 3rd season of ''Series/SonsOfAnarchy'' Samcro goes to Ireland to recover Jax's kidnapped son Abel and meet up with the Irish chapter of Samcro. While there Jax makes out with Trinity the step-daughter of one of Samcro's founders. It turns out Trinity's mother had an affair with Jax's father when he was in Ireland founding the Irish chapter and Trinity is the result.
* ''Series/TheXFiles'':
** We find out that Jeffrey Spender, who was working for CSM and managed to steal the X-Files from Mulder and Scully with Diana Fowley, is not only CSM's son but that CSM is also Mulder's biological father...making them half-brothers. Ouch. Presumably this revelation also makes Mulder's long lost sister Samantha his half-sister.
*** In Season 11, Scully's son William [[spoiler: who was believed to have been abandoned sometime before ''Film/TheXFilesIWantToBelieve'' takes place, is both alive and later discovered to]][[spoiler: not be Mulder's son. He is also CSM's boy, making William and Mulder Half-Brothers.]]
** Scully had a daughter she never knew about thanks to some ova-stealing.
* On ''Series/{{Alias}}'', Sydney discovers a long-lost sister, Nadia, at the end of season 3. Said sister goes on to: [[spoiler: become a series regular at the start of season 4, fall into an [[PutOnABus incurable]] [[ConvenientComa coma]] by the end of season 4, and is KilledOffForReal in season 5]]. A later episode reveals Nadia had another half-sister who was already deceased. Arvin and his wife Emily had a daughter named Jacqueline but she died in infancy. This was partly what triggered Arvin's obsession with the works of Milo Rambaldi.
* Turns out that ''Series/{{Dexter}}'' has a [[spoiler:brother]] he never knew about, who turns out to be the [[spoiler:Ice Truck Killer of the first season]].
* In ''Series/ThePretender'' Jarod founds out that he has a long lost brother Kyle and sister Emily. Ms. Parker founds out Mr. Lyle is her twin brother Mr. Lyle. Then there's Ethan who is the son of Jarod's father and Ms. Parker's mother. Oh and Mr. Lyle and Ms. Parker have another biological half-sibling, Mr. Raines daughter Annie.
* In ''Series/TrueBlood'', Vampire Bill discovers [[spoiler: after he's already started sleeping with one of them]] that the Bellefleur siblings are his great-great-great grandchildren.
* On ''Series/BoyMeetsWorld'', Shawn runs into his long-lost half brother Jack when Jack arrives in Philadelphia to go to college. Shawn knew he existed before this but they were so estranged that none of the other main characters (or the audience) knew about him.
* ''Series/MelrosePlace'':
** Jane finds out she is adopted and eventually connects with her birth mother.
** Sydney turns out to be Violet's mother in the relaunch.
** Amanda meets her long lost mother and half-brother before they are spun off onto Models Inc.
* On ''Series/BeverlyHills90210'' Donna finds out her cousin Gina is also her half-sister. Gina and Donna share the same father and their mothers are sisters.
** Dylan finds out after his father Jack's death that Jack fathered an illegitimate daughter named Erica. Many years after his father's death he finds out his father's death was staged and that he is remarried living under an assumed name and that he has a young son named Jack.
** Steve always knew he was adopted. When he finds his biological mother's father he also learns a surprising secret. His adopted father was his biological father all along. His father also had 2 other sons Austin and Ryan.
** Erin Silver isn't Kelly Taylor's only half-sibling. On her father's side she has a half-sister named Joy.
* Has reached epidemic levels in ''Series/{{Merlin|2008}}''; there's been Morgana's long-lost sister Morgause, Merlin's long-lost father Balinor, Guinevere's long-lost brother Elyan, and Arthur's long-lost uncle Agravaine ([[RememberTheNewGuy who has apparently been there all along]]). And then there's Morgana and Morgause's mother Vivianne, whose absence from the show is never explained.
* ''Series/{{JAG}}'': Harm spends a substantial portion of the show (seasons 1-3) searching for his father, who went MIA during UsefulNotes/TheVietnamWar. [[spoiler: His father escaped custody, and was later shot and killed, but not before meeting a Gypsy woman and fathering another son, Sergei.]]
* ''Series/TeenWolf'':
** In the third season we get to meet [[spoiler: Derek's younger sister Cora, who was thought to be killed in the Hale fire]].
** And in Season 3B we meet another long-lost Hale, [[spoiler: Peter's daughter Malia Tate, who even he didn't know he had]].
* In ''Series/RobinHood'', [[spoiler:Robin's father and Guy of Gisborne's mother were having an affair, making them... something]]. And there's also two previously unknown characters introduced as long lost siblings: [[spoiler: Isabella, Gisborne's long lost sister, and Archer, Gisborne ''and'' Robin's unknown half-brother]].
* This and SurpriseIncest are both {{subverted|Trope}} on the season 9 premiere of ''Series/HowIMetYourMother''. Robin and Barney, who are about to get married, realize they share a cousin. The audience is reminded that Barney found out a couple of seasons back that he's 1/4 Canadian. Luckily, they're not actually blood relatives.
* ''Series/{{Smallville}}'': A variation. Once [[BigBad Lex]] was off the show, new character [[TheBaroness Tess Mercer]] took his place as CEO of [=LuthorCorp=]. She seems [[SuspiciouslySimilarSubstitute very similar]] to Lex, especially in season 8, and she has much of his same [[ManipulativeBastard habits]]. Two and a half seasons after her introduction, it's revealed that the reason she seems so much like a Luthor is [[TheReveal because she is one]], as she finds out that she's Lionel's daughter. It's not a straight example because they weren't on the show at the same time, but it has a significant impact on the show and on Tess's character. (In the GrandFinale, Lex's clone reveals that [[{{Jerkass}} he knew the entire time]].)
* In season two of ''Series/{{Gotham}}'' Oswald meets his long-lost father [[spoiler:at his mothers grave]]. His father didn't know he had a son until that moment.
* In season 4 of ''Series/{{Elementary}}'', Joan meets her younger half-sister Lin. She originally met Joan as a client however Joan learned that they shared the same originally surname ("Yeun"). Lin however had never intended on telling Joan of their relationship and only came to her for help.
* On ''Series/WKRPInCincinnati'', Les got a "Dad is not your father" moment, finding out his biological father was still alive and was a barber in Kentucky (the man Les thought was his father was actually his step-father, and had passed away). Les goes to his barber shop and they have a conversation, but Les doesn't reveal who he is.
* It would be easier to list the characters on ''Series/OnceUponATime'' who don't find out they are related in some way.
* When the vampiric Barnabas Collins introduced himself to the Collins family on ''Series/DarkShadows'', he passed himself off as a long-lost cousin from the "English branch of the family." Strictly speaking that's absolutely true, just not quite how the Collins family took it.
* The ''Series/{{Dinosaurs}}'' episode "Into the Woods" had Roy Hess reveal that he was separated from his father Les at a young age. Near the end of the episode, he meets an elderly Tyrannosaurus named Les who mentions being separated from his son Roy years ago. The episode ends before the two make the connection.

[[folder:Mythology and Religion]]
* Myth/ClassicalMythology: Theatre/{{Oedipus|TheKing}}, long-lost son of Laios (whom he kills) and Iocaste (whom he marries). A pattern repeated with Telegonos, son of [[Literature/TheOdyssey Odysseus]] and Circe. He winds up accidentally killing his long-lost father, and in a creative instance of PairTheSpares, he marries Odysseus' widow Penelope, while Penelope's son Telemachus marries Circe.
* Morgan le Fay to Myth/KingArthur, who comes with extra disturbing quotient in the form of their mutual child he just sort of forgot about.
* {{Mahabharata}}: Much to their dismay, Arjun and his brothers come to find that [[TheDragon their sheming cousin's right hand man Karna]] is actually ''their older brother'', whom their mother abandoned after giving birth to him out of wedlock, leaving him to be brought up by low-ranking commoners & receive much mockery for his supposedly "low birth" despite [[TheAce his prowess as a warrior]]). They only find out after they've killed him in [[SuccessionCrisis a bloody, costly war of succession]].

[[folder:Professional Wrestling]]
* Wrestling/{{Kane}}, the long thought lost brother to Wrestling/TheUndertaker in Wrestling/{{WWE}}.

* Siegmund and Sieglinde find this out at the end of the first act of ''Theatre/DieWalkuere''. This does nothing to avert BrotherSisterIncest.
* ''Theatre/AFunnyThingHappenedOnTheWayToTheForum'': [[spoiler: Miles Gloriosus and Philia. Thankfully revealed before their arranged marriage can take place, let alone be consummated]].
* ''Theatre/IntoTheWoods''
** An interesting aversion of sorts, where the baker and Rapunzel are these, but neither realizes and nor does their being related have any effect on the plot.
** [[spoiler:The Mysterious Man]] also counts since he hasn't seen [[spoiler:The Baker]] since he was a baby/toddler. However, he does affect the First Act unlike his daughter.
* At the end of the opera ''Theatre/IlTrovatore'' an old gypsy reveals to the villain that he has just killed his long-lost brother. Since this is the last line of the libretto (and there are just 2 bars of music left to go), the baritone is reduced to making a face at the audience to express his dismay as the curtain comes down. And this troper has seen some truly ridiculous grimacing. Verdi must have been under deadline pressure.
* Played for laughs in ''Cox and Box'', where the ''absence'' of a strawberry mark on his left shoulder proved that Box was Cox's long-lost brother.

[[folder:Video Games]]
* [[spoiler:The Masked Man]] in ''VideoGame/{{Mother 3}}''. Though, really, if you didn't see it coming...
* ''[[VideoGame/SoulSeries Soulcalibur]]'': In ''Soulcalibur V'', [[spoiler:Xiba and Leixia are half-siblings. Xiba is the result of an affair between Xianghua and Kilik, while Leixia is the daughter of a Ming General; Xianghua married the latter per her family's request after finding out of her affair with Kilik. As of right now, neither of them know their relationship]].
* In ''VideoGame/FinalFantasyIV'', [[spoiler: Golbez is Cecil's long-lost brother]].
* In ''VideoGame/FinalFantasyV'', [[spoiler: Faris is Lenna's long-lost sister]].
* In ''VideoGame/FinalFantasyIX'', [[spoiler: Kuja, the game's main antagonist, turns out to be the long lost brother of our intrepid hero, Zidane. This drives a great deal of the game's plot]].
* In F.E.A.R., at the end [[spoiler: is revealed that the main character is not only the brother of Paxton Fettel, but also the son of Alma]].
* In ''VideoGame/TalesOfSymphonia'', [[spoiler: Kratos is Lloyd's father. Until Lloyd was seventeen Kratos basically thought he was dead]].
* Almost everybody with a sibling in ''[[VideoGame/FireEmblemElibe Fire Emblem: Blazing Sword]]'' seems to have been separated, but [[spoiler: Rebecca and Dan/Dart]] are the ones who fit this trope best.
** Also, Arthur and Tinny in ''[[VideoGame/FireEmblemJugdral Seisen no Keifu]]''. And Leif and Altenna in the same game. In both cases, the latter has to be convinced by their brother to do a HeelFaceTurn. Finally, we have a particularly sad case with Leen and Corple, who don't even ''know'' they're brother and sister.
** In ''Radiant Dawn'', [[spoiler: Micaiah is the long-lost older sister to Sanaki, and is thus also lost to their grandmother Misaha, and thus, lost to the PROGENITOR of their line Lehran AKA Sephiran, since he thought Micaiah had died]]. This example is unusual in that the revelation doesn't impact the story at all; by the time it comes out, the game is over and both sisters have accepted that the other has their own country to protect, but promise to work together as friends and allies. Other examples in [[VideoGame/FireEmblemTellius the same world]] include: Leanne to Reyson in ''Path Of Radiance'', then Rafiel to both in ''Radiant Dawn'', [[spoiler: Rajaion and his nephew Soren]] to the Dragon Laguz Royalty in ''Radiant Dawn'', and Ena to [[spoiler: her grandfather Nasir]] in ''Path Of Radiance'', as the sequel makes it clear it's been a while since they last saw each other.
* ''VideoGame/TheHangedMan'' has William Morton, who is the cousin of [[VideoGame/TheCrookedMan previous protagonist]] David Hoover. [[spoiler:They are actually not cousins, they are half-brothers. David's father had an affair with Will's mother and, when she got pregnant with his child, he decided to leave David and his mother.]]
* [[spoiler: K' and Sarah/Whip]] in ''VideoGame/TheKingOfFighters''.
* A mix of LukeIAmYourFather and dead big brother happens with ''VideoGame/ValkyriaChroniclesII'', when Avan and co. was desperately trying to defend the school from Rebel forces, a HeroicSacrifice by Juliana reveals that Leon is Dirk Gessernel, one of the three Gessernel siblings.
* In ''[[VideoGame/{{Onmyoji}} Onmyōji]]'' [[spoiler: Kagura is Hiromasa's long-lost sister]]
* In ''VideoGame/SidMeiersPirates'', you can purchase maps that lead to where your long lost sister is hidden on a plantation. Once you have rescued her, you can also find your long lost father, mother, brother, cousin, etc. They might give you a map that leads to lost Aztec treasure!
* Heavily implied in the first ''VideoGame/RuneFactory'' game. [[spoiler: Ivan is operating under the impression that you're his long lost brother, but doesn't act on his suspicions so that you can be happy.]]
* Non-protagonist example: In ''Rhiannon: Curse of the Four Branches'', it turns out that the guy you exchange e-mails with is [[spoiler: the long-lost son of a previous victim of the curse, who is reunited with his sister (off-screen) if you succeed]].
* Subverted (!) with Ivan in ''VideoGame/GoldenSun'' and ''VideoGame/GoldenSun: The Lost Age''. In the first game, he makes the acquaintance of spiritual leader and martial-arts master Hama, who acts as a mysterious mentor figure and refuses to bond closely any more than is needed to teach him to Reveal illusions. In the second game, Hama is revealed to be Ivan's sister... but neither one was ''lost'' to begin with: Ivan was sent away to be raised by non-Adepts so he would be in the right place at the right time to join Isaac's quest, and Hama has been discreetly keeping tabs on him the whole time, while pushing him away to keep her emotions from causing trouble. He's annoyed at this point, because she's the ''only blood relative he has'', he wants to learn more about his past/family/etc., and she's ''still'' pushing him away because [[ItSucksToBeTheChosenOne his destiny isn't done yet]].
* ''SupplementalMaterial/TeamFortress2'' has Gray Mann, long lost brother of Redmond and Blutarch Mann and third son of Zepheniah Mann. When he was born, he was supernaturally intelligent and ugly; practically crippled in manliness compared to his brothers, yet somehow perfectly fluent in English (and discovered mathematical breakthroughs ''in the womb''). This disgusted Zepheniah, and he wanted the prodigy killed, but Gray was abducted and raised by an eagle (what it actually was is unknown). After learning the ways of the eagles, he betrayed his adopted family, killed his stepmother and stepsiblings, and ate them all before going back to civilization to build his empire. 150 years later, he murdered his brothers and plotted to take over Mann Co. with his robot army, leading to the "[[ManVersusMachine Mann Vs. Machine]]" game mode.
* In ''VideoGame/{{Homeworld}}'' [[spoiler:the Kadeshi are this to the Kushan on a species-wide level...which is discovered ''[[PlayerPunch after]]'' [[NiceJobBreakingItHero their fleet and habitat ships are decimated]]]].
* ''VideoGame/DisgaeaDimension2'' introduces Laharl's younger sister Sicily and Etna's older brother Xenolith.
** Sicily is introduced by retconning Laharl's mother death - she still died after giving ger mana to cure Laharl's illness, but she was pregnant with Sicily and had the choice to become an angel, but Sicily wouldn't survive, or pass the angel bliss to Sicily, but dying in the process.
** Xenolith is introduced revealing that Etna was actually born with a immense magic power inside her that would lead to her death, but her older brother decided to merge himself with a magic-absorbing artifact to take most of Etna's own magic, so she could survive. He then left Etna to Krichevskoy's care.
* The inciting villain of ''VideoGame/AvencastRiseOfTheMage'' and the player character spend so much time opposing each other, the reveal that they're siblings is hardly a surprise.
* In ''VideoGame/ShadowHearts: Covenant'', this happens more than once.
** Yuri and Kurando learn they are cousins, after several adventures together. It doesn't come as too much of a surprise, since both share Fusion powers and the same red eyes.
** Kallen turns out to be [[spoiler: Yuri's mother]], as a result of a StableTimeLoop.
** Nicolai and Anatasia are half-siblings, though she never learns about their relationship.

[[folder:Visual Novels]]
* [[spoiler: Apollo and Trucy]] in ''VisualNovel/ApolloJusticeAceAttorney''. Though as of right now, there is still no sign that the two of them know about it.
** Another example happens in ''[[VisualNovel/PhoenixWrightAceAttorney Trials and Tribulations.]]'' In the last case not only do we find out that [[spoiler: victim Elise Deauxnim was Mia and Maya Fey's long-lost mother (and Pearl's aunt), but serial killer Dahlia Hawthorne is Morgan Fey's long-lost daughter and Pearl's half-sister...as is Dahlia's twin sister Iris]].
* Hoo boy, ''VisualNovel/{{Ever17}}''. [[spoiler: Of the people on [=LeMU=], Sara and the Kid are fraternal twins. And they're the children of Tsugumi, on [=LeMU=] at the same time, and Takeshi, who's the other main character.]]

* [[spoiler:Trudy and Sharon]] in ''Webcomic/GeneralProtectionFault''.
* Blue and Isaac in ''Webcomic/NamirDeiter'' - Blue was four years old when their mother kicked his father out. Issac didn't know about his ''other'' sister, Roxanne (who had already left home when the elder Deiter met his father). They've since all gotten to know each other.
* ''Webcomic/GirlGenius'' has [[spoiler:Zola la Sirène Dorée]] who was heavily implied (good resemblance) to be a relative of [[spoiler:[[http://www.girlgeniusonline.com/comic.php?date=20090408 Lucrezia]]]] and thus [[spoiler:[[http://www.girlgeniusonline.com/comic.php?date=20090701 Agatha.]]]] And eventually was revealed to be [[spoiler:[[http://www.girlgeniusonline.com/comic.php?date=20100625 Lucrezia's niece.]]]]
** Zeetha was implied to be [[spoiler: Klaus' daughter, and by extension Gil's sister]].
** Theo and Agatha found out early on that they are cousins. Theo was very happy about the revelation, since he has no other living relatives.
* ''Webcomic/{{Homestuck}}'': [[spoiler: John and Jade]] are HalfIdenticalTwins, as are [[spoiler: Rose and Dave]], and they were split up via the Reckoning. This reveal had the side effect of [[ShipSinking sinking two of the biggest ships in the fandom]].
* In ''Webcomic/{{Glorianna}}'', Hope is [[spoiler:Glorianna's daughter]], abandoned as a baby and ''RaisedByOrcs'' to be a fanatical cultist.
* In ''Webcomic/ElGoonishShive'', hints are increasingly being dropped that Susan and Diane are this, since they're physically identical[[note]]Despite appearances this also applies to hair color, since they're both natural blondes and Susan's hair is dyed[[/note]] and were born 20 minutes apart on the same day. Later [[http://www.egscomics.com/index.php?id=1699 confirmed]], and even later revealed that Diane is aware of their relationship, though Susan seems to have no idea whatsoever.
* ''Webcomic/KevinAndKell'''s Corrie was eventually revealed to be the long-lost daughter of Ralph Dewclaw.
* Double subverted with Anak and Androssi Zahard from ''Webcomic/TowerOfGod''. [[spoiler: At first they seem like adoptive sisters, but then it turns out that Anak is not a real Princess of Zahard. She is the rumored daughter of Androssi's sister. Meaning that Anak is Androssi's niece even though Anak is older]]

[[folder:Western Animation]]
* ''WesternAnimation/MickeyMouse'' - Remember WesternAnimation/OswaldTheLuckyRabbit? You probably don't. He's Mickey's long-lost older half-brother. Walt Disney created him before Mickey, and he laid the groundwork for Mickey's rise to stardom. Disney ultimately addressed Oswald's return in ''VideoGame/EpicMickey''.
* From the standpoint of every other toon on The Warner Lot, ''WesternAnimation/{{Animaniacs}}'' Yakko, Wakko and Dot are Long Lost Siblings. But the truth is they were locked in the water tower because they're completely nuts.
* Kevin's stepfather shows up in the finale for season 1 of ''WesternAnimation/Ben10UltimateAlien'' -- he's been with Kevin's mother since the ''WesternAnimation/{{Ben 10}}'' days, but this is the first time he appears onscreen.
* In ''WesternAnimation/DonkeyKongCountry'', the ChristmasEpisode reveals that Klump's long-lost brother is Captain Skurvy, who was exiled from their family home when Klump created a firework accident and Skurvy took the fall.
* In the third season of ''WesternAnimation/DragonsRidersOfBerk'', it turns out that [[spoiler:Heather is actually the long-lost sister of Dagur the Deranged.]] This causes a bit of awkwardness, since [[spoiler:Dagur is not only responsible for the death of their biological father, but also burned down Heather's village and killed her adoptive parents. Also, he's a completely AxCrazy lunatic.]]
* In a post-Poof episode of ''WesternAnimation/TheFairlyOddParents'', it turns out that [[TheDitz Cosmo]] and [[TheAhnold Jorgen von Strangle]] are cousins, and that fact was kept a secret for obvious reasons. Bonus points if you throw in TalkingToHimself, since both characters are voiced by Creator/DaranNorris.
* In ''WesternAnimation/FamilyGuy'', Lois has a long lost brother Patrick who was put in a mental hospital.
* Hank of ''WesternAnimation/KingOfTheHill'' was revealed to have a Japanese half-brother.
* [[WesternAnimation/HeManAndTheMastersOfTheUniverse1983 He-Man]] happens to have a twin sister from whom he was SeparatedAtBirth. Hordak attempted to kidnap them both due to a prophecy but was only able to get Adora. This backfires when Adora, learns her true heritage, does a HeelFaceTurn and becomes WesternAnimation/SheRaPrincessOfPower.
* The ChristmasEpisode of ''WesternAnimation/HeyArnold'' features the [[spoiler:reunion of Mr. Hyunh and his long-lost daughter]].
* In the ''WesternAnimation/PhineasAndFerbStarWars'' special (where Phineas is a young rebel while Candace is a stormtrooper). Before the Death Star explodes, Phineas regrets not being reunited with his big sister who had left Tatooine when he was a baby. Only then Candace realizes that the young rebel is her brother, Phineas, and they embrace each other.
* PunkyBrewster finds out she has an aunt and an uncle in the animated episode "Punky The Heiress." They're actually servants for the Chester Henderson mansion. They disguise Punky as Chester's granddaughter and use her to embezzle the granddaughter's inheritance from the missing Henderson patriarch.
* ''WesternAnimation/SamuraiJack'': In the 2017 Season Five, Aku discovers he has a long lost [[spoiler: daughter. Ashi, born of the High Priestess of the Daughters of Aku cult, who drank Aku's essence and apparently bore six daughters from doing so. They're raised to hate Jack and when sent to kill him, only Ashi survives.]] When Aku finds out, he promptly possesses them and uses them to attack Jack.
* ''WesternAnimation/TheSecretSaturdays'': Drew yoinks off the helmet from [=VanRook=]'s apprentice, gets a look at his face, and has a {{flashback}} which makes her realize he's her brother, which leads to his HeelFaceTurn.
* ''WesternAnimation/TheSimpsons''.
** Homer's brother Herb and a long-lost half-sister in England.
** Herb was raised in an orphanage run by Dr. Hibbert's long-lost brother. In "Round Springfield" it was then revealed that Bleeding Gums Murphy was the long-lost third Hibbert brother.
** "The Simpsons Spin-Off Showcase": [[JumpingTheShark "And did someone say, 'long-lost triplets?'"]]
* Eric Cartman from ''WesternAnimation/SouthPark'' finds out his old ginger nemesis Scott Tenorman is his half-brother in the episode "201". Eric had previously orchestrated the murder of Scott's parents (and thus Eric's own father) and tricked Scott into eating their remains at the Chili Con Carnival. When Eric finds out he becomes depressed...[[RedheadedStepChild at the thought of being half-ginger, though he does cheer up when he realizes he's also half-Denver Bronco.]]
* ''[[WesternAnimation/TeenageMutantNinjaTurtles2012 TNMT (2012)]]'': It turns out Miwa, Splinter's long lost daughter whom he believed was murdered by The Shredder when the latter murdered Splinter's wife, is not only still alive, but [[spoiler: is actually Karai]].
* Hank Venture from ''WesternAnimation/TheVentureBrothers'' finds out that his best friend Dermott Fictel is the illegitimate son of his father Rusty Venture and Nikki Fictel. Nikki Fictel was a teenager when Dermott was born and Dermott was raised to believe Nikki was his sister and his grandmother was his mother. Hank finds this out shortly AFTER losing his virginity to Nikki but has his memory wiped.
* 4Kids editing of ''WesternAnimation/WinxClub'' provides an example of this trope being [[ExecutiveMeddling undermined by editing]]: The Trix exposit about the Dragonfire to Bloom. [[spoiler: Of their ancestors' attempt to take it, they say, "Your sister ruined everything by saving your life." This prompts Bloom to say, "Daphne?" But in the dub, the Trix never mention this, instead referring to Daphne as "the guardian of the flame", with Bloom saying "Daphne?" being cut out. It's rather awkward, since the first time it's indicated that they're sibs in the dub is when she's looking at her family tree in S2.]]
* WesternAnimation/StevenUniverse: In Gem Harvest, we get to meet the first member of Greg's family: Cousin Andy, who has not been around because he's been flying his antique plane all over the world.
* In the MultiPartEpisode "Power of Four" from ''WesternAnimation/ThePowerpuffGirls2016'', the girls learn that they have an older sister who was thought to have died in an explosion she created through PowerIncontinence, but in truth she just exiled herself from Townsville for years.
* For much of seasons 3 and 4 of ''WesternAnimation/{{Detentionaire}}'', Lee is menaced by the Serpent, an assassin working for MWF that seems to have his own agenda in addition to carrying out their orders. Come "Mummy Ping and the Snake Man of Evil" and we find out that [[spoiler: the Serpent is actually Lee's older brother, who was taken from his parents in order to serve MWF's needs. His own agenda? Stalking Lee's family in order to confirm this.]]