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* ''Series/TheBoys'': In a twist true to the spirit of comic book superheroes, [[spoiler: Soldier Boy is revealed to be Homelander's father and thus Ryan (a ChildOfRape)'s grandfather. Rather than a bonding moment Soldier Boy deems them both [[InadequateInheritor Inadequate Inheritors]] due to not raising them himself. This in turn makes Butcher breaks his deal with Soldier Boy to protect Ryan.]]
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* ''Series/RedDwarf'':
** Lister learns in the first season he has twin sons, [[MrSeahorse giving birth to them himself]] after his DistaffCounterpart impregnated him. Still that's nothing compared to Season 7 where it's revealed [[spoiler:Lister is his own son with Kochanski being his mother.]]
** Addressed and hilariously defied in ''Recap/RedDwarfBackToEarth'' after overpowering their creator, GenreSavvy ButtMonkey Rimmer demands he get a happy ending.
-->'''Rimmer''': I save the day. I get a girlfriend who's gorgeous and crazy about me. And before you even think of it, after we've bonked each other senseless, she doesn't turn out to be my long-lost sister.
-->'''Creator''': Damn. How did you know I was thinking that?
-->'''Rimmer''': Because I know how ''you'' think.
** In ''Recap/RedDwarfThePromisedLand'' it's revealed the BigBad Roden [[spoiler:is Cat's long lost older brother with Roden being very confused as to why his little brother looks older than him. Cat explains just the thought having to do work aged him beyond his years. It's also left unexplained how Roden could still be alive considering the 200 years difference while Cat and Lister were in hibernation, though it's inferred Felis sapiens are LongLived.]]
** Lister learns in the first season he has twin sons, [[MrSeahorse giving birth to them himself]] after his DistaffCounterpart impregnated him. Still that's nothing compared to Season 7 where it's revealed [[spoiler:Lister is his own son with Kochanski being his mother.]]
** Addressed and hilariously defied in ''Recap/RedDwarfBackToEarth'' after overpowering their creator, GenreSavvy ButtMonkey Rimmer demands he get a happy ending.
-->'''Rimmer''': I save the day. I get a girlfriend who's gorgeous and crazy about me. And before you even think of it, after we've bonked each other senseless, she doesn't turn out to be my long-lost sister.
-->'''Creator''': Damn. How did you know I was thinking that?
-->'''Rimmer''': Because I know how ''you'' think.
** In ''Recap/RedDwarfThePromisedLand'' it's revealed the BigBad Roden [[spoiler:is Cat's long lost older brother with Roden being very confused as to why his little brother looks older than him. Cat explains just the thought having to do work aged him beyond his years. It's also left unexplained how Roden could still be alive considering the 200 years difference while Cat and Lister were in hibernation, though it's inferred Felis sapiens are LongLived.]]
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** 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 husband's but was somehow transformed by the pah wraiths as part of their covenant. Kira doesn't buy it.
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** [[Characters/StarTrekDeepSpaceNineGulDukat Gul Dukat 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 husband's but was somehow transformed by the pah wraiths as part of their covenant. Kira doesn't buy it.
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* ''Series/MonarchLegacyOfMonsters'': Half-siblings Cate and Kentaro Randa to each-other, due to their [[SecretOtherFamily shared father's double-life]] which only comes to light when the both of them are young adults and their father is [[DisappearedDad presumed dead]].
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* 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.
* 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.
* ''Series/AlmostFamily'': Due to Leon's fraud, it turns out that Julia, Amanda, and Edie along with all the many other children he's fathered are this for each other. Much of the plot involves them meeting each other, forging bonds and continually meeting yet another long-lost half-sibling.
* ''Series/TheAmazingRace'': Season 34 of the American series features a long-lost set of identical twins, Molly and Emily. Both were adopted as babies from Korea and only found out about each other the year previously when Emily’s daughter did a DNA test and Molly popped up as a close relative.
* ''Series/{{Arrow}}'':
** Thea Queen finds out that her father is not Robert Queen, but Malcolm Merlyn, which means that Tommy is her half-brother. The catch is that by the time she learns this, Tommy is already dead.
** In Season 7, Oliver learns that while his mother was having an affair with Malcolm, his father was having an affair with a Japanese woman named Kazumi Adachi, who conceived a daughter, Emiko. Unlike Thea however, Emiko was raised in poverty, causing her to become TheResenter towards the Queen family.
** Oliver's children, William Clayton and Mia Smoak, don't learn about their relationship until adulthood, as the latter's existence is a secret known only to select people in Oliver's inner circle, while William was raised by his grandparents, who disliked Oliver's vigilantism.
* ''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.
* ''Series/Batwoman2019'': In Season 3 Ryan discovers she has a half-brother by her birth mother.
* 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 (which would also make them three-quarter siblings).
** 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.
* Howard from ''Series/TheBigBangTheory'' discovers he has a half-brother, the product of a relationship his father had after he walked out on Howard and his mother.
* ''{{Series/Bonekickers}}'': It's revealed that Vic is Magwilde's half-sister, as they share the same birth mother. This is mostly unexplored due to the series getting cancelled
* ''{{Series/Bones}}'':
** Brennan's parents disappeared when she was young, causing her to be put into foster care and become estranged from her older brother Russ (he was too old for foster care but too young to care for her himself). She's reunited with her father and brother during the course of the series and, [[PlayingWithATrope if you want to stretch the definition a bit]], discovers that a set of remains that's been in Limbo since she got to the Jeffersonian belongs to her mother.
** Brennan’s dad invited her cousin to come for Christmas. Brennan hadn’t met her before.
** Hodgins finds out that he isn’t an only child like he always thought. He has a brother, Jeffery, who lives in a mental institution. Jeffery has a schizoaffective disorder that causes him to have violent outbursts and they worried for baby Jack’s safety. Probably justified given families in his parents’ time were told to basically forget that institutionalized children existed...even other children weren’t always told. Plus they were a wealthy, well known family and might have considered Jeffery a dark spot on their reputation.
* 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/BurdenOfTruth'': Luna turns out to be [[spoiler:Joanna's half-sister on her father's side]].
* ''Series/Charmed1998'':
** The girls' father is introduced in this manner. He comes to Prue to anonymously get an heirloom ring appraised and waits for her to recognize it before revealing his identity.
** 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 which had fortunately been 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.
* ''Series/ChasingLife'': Natalie is the half-sister of April and Brenna due to the affair their father had, whom they don't meet until after he dies. It turns out that their mother and grandparents already knew about Natalie though.
* ''Series/CityOnAHill'': Jenny learns of her long lost half brother only well into adulthood, as he was born due to a secret affair her father had.
* Mac Taylor meets a young man in Season 3 of ''{{Series/CSINY}}'' who is revealed to be his stepson. His wife got pregnant in high school and placed the boy up for adoption. She talked about finding him but died on 9/11. Though Reed initially rebuffs Mac's attempt at a connection when he learns Claire is dead, the two do eventually build a friendship.
* 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.
* 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.
* 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]].
* 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.
* ''Series/DoctorWho'': In [[Recap/DoctorWhoS30E7TheUnicornAndTheWasp "The Unicorn and the Wasp"]], the villain is the secret illegitimate son of [[spoiler:Lady Eddison]], who had given him up after he was born to avoid the scandal.
* ''Series/DueSouth'''s Constable Benton Fraser meets his half-sister in the show's penultimate episode.
* 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 original surname ("Yeun"). Lin however had never intended on telling Joan of their relationship and only came to her for help.
* ''Series/{{The Flash|2014}}'': In season 2, Iris and Joe learn that Francine was pregnant when she left Joe, which means Iris has a brother she never knew about. Said brother is [[Characters/TheFlashWallyWest Wally West]], who becomes a speedster like Barry.
* In the pilot episode of ''Frankie Drake Mysteries'', the title character learns the industrialist's wife she's investigating is actually her mother, who "died" when she was four years old.
* ''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 gave birth to her only living daughter Daenerys approximately 8 to 9 months after [[spoiler: Lyanna Stark gave birth to her son Jon, resulting in Jon being slightly older than Daenerys.]] Dramatically enough, Maester Aemon and [[spoiler: Jon]] bonded over their families being in trouble (Aemon with his Targaryen family and [[spoiler: 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 [[spoiler: they share their own family tie via their Targaryen blood.]]
* ''Series/GhostsUK'': [[spoiler: {{Subverted}}. A woman named Lucy appears in the episode "A Lot To Take In" claiming to be Alison's long-lost sister from a previous relation that her father had. However, it is revealed in the last episode of the season that she was only pretending so she can take Alison's money.]]
* 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.
** Later, Rose meets a monk who turns out to be her birth father.
* In Season 2 of ''Series/{{Gotham}}'' Oswald meets his long-lost father [[spoiler:at his mother's grave]]. His father didn't know he had a son until that moment.
* ''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.
* 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.
* 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/{{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.]]
* The premise of ''Series/JejakSuaraAdzan'' is about Dimas trying to find his long-lost older brother Dika, who had been adopted by another family when Dimas is an infant. The series drops clues and eventually reveals that [[spoiler:Putra, who has been helping Dimas find Dika, is Dika himself all along, without anyone realizing it until the finale because Dika's adopted parents changed his name to Putra when he is three-years old.]]
* ''Franchise/KamenRider'':
** ''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/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/LAsFinest'': Syd learns she has an adult half-sister as a result of her dad cheating with another woman on her mom. Further, she has a niece and nephew, her half-sister's kids.
* 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; Dr. Huang points out that it is physiologically impossible to fake that kind of reaction. [[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/LegendOfTheSeeker'': Richard learns he has a half-sister he never knew about, Jennsen.
* ''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/TheLWord'':
** After reconnecting with her estranged dad, Shane finds out she has a brother, Shay, from his second wife. [[spoiler:Eventually she has to care for him as his mom leaves him with Shane.]]
** In ''Generation Q'' Angelica does a DNA search and finds she's got a half-sister as they share the same birth father (who had been her mother's sperm donor).
* ''Series/MakoMermaidsAnH2OAdventure'': In late season two Zac discovers [[spoiler:that not only is he adopted and a real merman, but he is also the long lost of Mimmi.]]
* ''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.
* 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/{{Monk}}'' discovers he has a long lost brother.
* ''Series/Mouse2021'': Michaela, the girl at the orphanage, is really Jae-hoon/Ba-reum's sister Jae-hee.
* Detective William Murdoch of ''Series/MurdochMysteries'' discovers that he has a half-brother in the Season 2 finale.
* ''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 two 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.
* Played with in an episode of the short lived Creator/JohnGoodman vehicle ''Normal, Ohio.'' His character's [[DadTheVeteran father]] admitted to having an affair with a woman that "could melt butter on her ass" [[UsefulNotes/TheKoreanWar while serving in Korea,]] and while being engaged to his current wife. When she admitted to having an affair he gave her hell for it, while not mentioning his own indiscretion. At the ned when the situation was resolved, without admitting to the affair, Goodman's character calls his parents' house while they're out and leaves a message in their answering machine in [[AsianSpeekeeEngrish a heavily accented, high pitched voice]] claiming to be the woman he slept with, and that she will be bringing her adult twin sons to meet their father for the first time.
* ''Series/NoughtsAndCrosses'': Yaro turns out to be the half-brother who [[spoiler:Sephy and Minerva]] had not known they had.
* Nichols family patriarch Caleb Nichols has an illegitimate daughter named Lindsay on ''Series/TheOC'' in addition to his two other daughters Kirsten and Hailey.
* It would be easier to list the characters on ''Series/OnceUponATime'' who don't find out they are related in some way.
* ''Series/TheOutpost'':
** A man claiming he's Gwynn's brother arrives at the Outpost. [[spoiler: It turns out that he's a fake.]]
** [[spoiler:Naya]] turns out to be [[spoiler:Janzo]]'s sister.
* ''{{Series/Pandora}}'': [[spoiler:Tierney]] it turns out is Jax's mother's birth daughter. Since Jax is adopted, her mother says they're therefore "kind of sisters".
* In ''Series/ThePretender'' Jarod finds out that he has a long lost brother Kyle and sister Emily. Ms. Parker founds out Mr. Lyle is her twin brother. 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' late daughter Annie.
* ''Series/PrincessSilver'':
** Fu Chou is [[spoiler: Wu You's twin brother]]. He doesn't react well when he learns the truth.
** Hen Xiang is [[spoiler: Rong Le's sister]]. This doesn't cause nearly as much angst when it's revealed.
* ''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/ReservationDogs'': In "Elora's Dad" Elora finally meets Rick, her birth father, and discovers that she also has three half-siblings who are very happy to have an older sister.
* 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.
* ''Series/{{Riverdale}}'':
** The first season's penultimate episode reveals that Polly Cooper's great-grandfather was a brother to Jason Blossom's great-grandfather; he was born Blossom, but changed it to Cooper. This means that not only are [[SurpriseIncest Polly and Jason third cousins]], so are Betty and Cheryl.
** Betty later finds out that she has a brother she didn't know about. Alice and Hal conceived a baby boy when they were still in high school, whom they gave up for adoption. The brother, Charles "Chic", appears in season 2, but it turns out that he is an impostor, as the real Charles had died. Only for the season 3 finale to reveal that Charles is still alive -- and in a relationship with Chic.
* 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]].
* 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!
* On ''Series/SixFeetUnder'' George Sibley's illegitimate son Kyle was a bit bitter and sent his father boxes of feces.
* ''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 the third 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/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 husband's 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/{{Supernatural}}'':
** In the fourth 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/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/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.
* ''Series/TheVampireDiaries'':
** [[IdenticalGrandson Katherine is Elena's great-great...grandmother.]]
** Alaric, due to his marriage to Isobel is Elena's stepfather.
* ''Series/{{Willow}}'': Scorpia, leader of the [[BanditClan Bone Reavers]], is revealed as Jade's long-lost older sister. Jade previously had believed her entire birth family was dead.
* 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.
* ''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 son, making William the half-brother to Mulder and Jeffrey.]]
*** [[spoiler: At the end of the series, it was revealed that Scully was pregnant again this time with Mulder's child. If she carries to term and gives birth, the child would be William's maternal half-sibling but paternal half-nephew or niece as well as CSM's grandchild.]]
** Scully had a daughter she never knew about thanks to some ova-stealing. [[spoiler:Unfortunately, she only knows her briefly since before her death.]]
----
* 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.
* ''Series/AlmostFamily'': Due to Leon's fraud, it turns out that Julia, Amanda, and Edie along with all the many other children he's fathered are this for each other. Much of the plot involves them meeting each other, forging bonds and continually meeting yet another long-lost half-sibling.
* ''Series/TheAmazingRace'': Season 34 of the American series features a long-lost set of identical twins, Molly and Emily. Both were adopted as babies from Korea and only found out about each other the year previously when Emily’s daughter did a DNA test and Molly popped up as a close relative.
* ''Series/{{Arrow}}'':
** Thea Queen finds out that her father is not Robert Queen, but Malcolm Merlyn, which means that Tommy is her half-brother. The catch is that by the time she learns this, Tommy is already dead.
** In Season 7, Oliver learns that while his mother was having an affair with Malcolm, his father was having an affair with a Japanese woman named Kazumi Adachi, who conceived a daughter, Emiko. Unlike Thea however, Emiko was raised in poverty, causing her to become TheResenter towards the Queen family.
** Oliver's children, William Clayton and Mia Smoak, don't learn about their relationship until adulthood, as the latter's existence is a secret known only to select people in Oliver's inner circle, while William was raised by his grandparents, who disliked Oliver's vigilantism.
* ''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.
* ''Series/Batwoman2019'': In Season 3 Ryan discovers she has a half-brother by her birth mother.
* 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 (which would also make them three-quarter siblings).
** 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.
* Howard from ''Series/TheBigBangTheory'' discovers he has a half-brother, the product of a relationship his father had after he walked out on Howard and his mother.
* ''{{Series/Bonekickers}}'': It's revealed that Vic is Magwilde's half-sister, as they share the same birth mother. This is mostly unexplored due to the series getting cancelled
* ''{{Series/Bones}}'':
** Brennan's parents disappeared when she was young, causing her to be put into foster care and become estranged from her older brother Russ (he was too old for foster care but too young to care for her himself). She's reunited with her father and brother during the course of the series and, [[PlayingWithATrope if you want to stretch the definition a bit]], discovers that a set of remains that's been in Limbo since she got to the Jeffersonian belongs to her mother.
** Brennan’s dad invited her cousin to come for Christmas. Brennan hadn’t met her before.
** Hodgins finds out that he isn’t an only child like he always thought. He has a brother, Jeffery, who lives in a mental institution. Jeffery has a schizoaffective disorder that causes him to have violent outbursts and they worried for baby Jack’s safety. Probably justified given families in his parents’ time were told to basically forget that institutionalized children existed...even other children weren’t always told. Plus they were a wealthy, well known family and might have considered Jeffery a dark spot on their reputation.
* 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/BurdenOfTruth'': Luna turns out to be [[spoiler:Joanna's half-sister on her father's side]].
* ''Series/Charmed1998'':
** The girls' father is introduced in this manner. He comes to Prue to anonymously get an heirloom ring appraised and waits for her to recognize it before revealing his identity.
** 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 which had fortunately been 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.
* ''Series/ChasingLife'': Natalie is the half-sister of April and Brenna due to the affair their father had, whom they don't meet until after he dies. It turns out that their mother and grandparents already knew about Natalie though.
* ''Series/CityOnAHill'': Jenny learns of her long lost half brother only well into adulthood, as he was born due to a secret affair her father had.
* Mac Taylor meets a young man in Season 3 of ''{{Series/CSINY}}'' who is revealed to be his stepson. His wife got pregnant in high school and placed the boy up for adoption. She talked about finding him but died on 9/11. Though Reed initially rebuffs Mac's attempt at a connection when he learns Claire is dead, the two do eventually build a friendship.
* 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.
* 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.
* 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]].
* 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.
* ''Series/DoctorWho'': In [[Recap/DoctorWhoS30E7TheUnicornAndTheWasp "The Unicorn and the Wasp"]], the villain is the secret illegitimate son of [[spoiler:Lady Eddison]], who had given him up after he was born to avoid the scandal.
* ''Series/DueSouth'''s Constable Benton Fraser meets his half-sister in the show's penultimate episode.
* 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 original surname ("Yeun"). Lin however had never intended on telling Joan of their relationship and only came to her for help.
* ''Series/{{The Flash|2014}}'': In season 2, Iris and Joe learn that Francine was pregnant when she left Joe, which means Iris has a brother she never knew about. Said brother is [[Characters/TheFlashWallyWest Wally West]], who becomes a speedster like Barry.
* In the pilot episode of ''Frankie Drake Mysteries'', the title character learns the industrialist's wife she's investigating is actually her mother, who "died" when she was four years old.
* ''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 gave birth to her only living daughter Daenerys approximately 8 to 9 months after [[spoiler: Lyanna Stark gave birth to her son Jon, resulting in Jon being slightly older than Daenerys.]] Dramatically enough, Maester Aemon and [[spoiler: Jon]] bonded over their families being in trouble (Aemon with his Targaryen family and [[spoiler: 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 [[spoiler: they share their own family tie via their Targaryen blood.]]
* ''Series/GhostsUK'': [[spoiler: {{Subverted}}. A woman named Lucy appears in the episode "A Lot To Take In" claiming to be Alison's long-lost sister from a previous relation that her father had. However, it is revealed in the last episode of the season that she was only pretending so she can take Alison's money.]]
* 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.
** Later, Rose meets a monk who turns out to be her birth father.
* In Season 2 of ''Series/{{Gotham}}'' Oswald meets his long-lost father [[spoiler:at his mother's grave]]. His father didn't know he had a son until that moment.
* ''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.
* 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.
* 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/{{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.]]
* The premise of ''Series/JejakSuaraAdzan'' is about Dimas trying to find his long-lost older brother Dika, who had been adopted by another family when Dimas is an infant. The series drops clues and eventually reveals that [[spoiler:Putra, who has been helping Dimas find Dika, is Dika himself all along, without anyone realizing it until the finale because Dika's adopted parents changed his name to Putra when he is three-years old.]]
* ''Franchise/KamenRider'':
** ''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/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/LAsFinest'': Syd learns she has an adult half-sister as a result of her dad cheating with another woman on her mom. Further, she has a niece and nephew, her half-sister's kids.
* 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; Dr. Huang points out that it is physiologically impossible to fake that kind of reaction. [[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/LegendOfTheSeeker'': Richard learns he has a half-sister he never knew about, Jennsen.
* ''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/TheLWord'':
** After reconnecting with her estranged dad, Shane finds out she has a brother, Shay, from his second wife. [[spoiler:Eventually she has to care for him as his mom leaves him with Shane.]]
** In ''Generation Q'' Angelica does a DNA search and finds she's got a half-sister as they share the same birth father (who had been her mother's sperm donor).
* ''Series/MakoMermaidsAnH2OAdventure'': In late season two Zac discovers [[spoiler:that not only is he adopted and a real merman, but he is also the long lost of Mimmi.]]
* ''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.
* 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/{{Monk}}'' discovers he has a long lost brother.
* ''Series/Mouse2021'': Michaela, the girl at the orphanage, is really Jae-hoon/Ba-reum's sister Jae-hee.
* Detective William Murdoch of ''Series/MurdochMysteries'' discovers that he has a half-brother in the Season 2 finale.
* ''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 two 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.
* Played with in an episode of the short lived Creator/JohnGoodman vehicle ''Normal, Ohio.'' His character's [[DadTheVeteran father]] admitted to having an affair with a woman that "could melt butter on her ass" [[UsefulNotes/TheKoreanWar while serving in Korea,]] and while being engaged to his current wife. When she admitted to having an affair he gave her hell for it, while not mentioning his own indiscretion. At the ned when the situation was resolved, without admitting to the affair, Goodman's character calls his parents' house while they're out and leaves a message in their answering machine in [[AsianSpeekeeEngrish a heavily accented, high pitched voice]] claiming to be the woman he slept with, and that she will be bringing her adult twin sons to meet their father for the first time.
* ''Series/NoughtsAndCrosses'': Yaro turns out to be the half-brother who [[spoiler:Sephy and Minerva]] had not known they had.
* Nichols family patriarch Caleb Nichols has an illegitimate daughter named Lindsay on ''Series/TheOC'' in addition to his two other daughters Kirsten and Hailey.
* It would be easier to list the characters on ''Series/OnceUponATime'' who don't find out they are related in some way.
* ''Series/TheOutpost'':
** A man claiming he's Gwynn's brother arrives at the Outpost. [[spoiler: It turns out that he's a fake.]]
** [[spoiler:Naya]] turns out to be [[spoiler:Janzo]]'s sister.
* ''{{Series/Pandora}}'': [[spoiler:Tierney]] it turns out is Jax's mother's birth daughter. Since Jax is adopted, her mother says they're therefore "kind of sisters".
* In ''Series/ThePretender'' Jarod finds out that he has a long lost brother Kyle and sister Emily. Ms. Parker founds out Mr. Lyle is her twin brother. 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' late daughter Annie.
* ''Series/PrincessSilver'':
** Fu Chou is [[spoiler: Wu You's twin brother]]. He doesn't react well when he learns the truth.
** Hen Xiang is [[spoiler: Rong Le's sister]]. This doesn't cause nearly as much angst when it's revealed.
* ''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/ReservationDogs'': In "Elora's Dad" Elora finally meets Rick, her birth father, and discovers that she also has three half-siblings who are very happy to have an older sister.
* 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.
* ''Series/{{Riverdale}}'':
** The first season's penultimate episode reveals that Polly Cooper's great-grandfather was a brother to Jason Blossom's great-grandfather; he was born Blossom, but changed it to Cooper. This means that not only are [[SurpriseIncest Polly and Jason third cousins]], so are Betty and Cheryl.
** Betty later finds out that she has a brother she didn't know about. Alice and Hal conceived a baby boy when they were still in high school, whom they gave up for adoption. The brother, Charles "Chic", appears in season 2, but it turns out that he is an impostor, as the real Charles had died. Only for the season 3 finale to reveal that Charles is still alive -- and in a relationship with Chic.
* 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]].
* 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!
* On ''Series/SixFeetUnder'' George Sibley's illegitimate son Kyle was a bit bitter and sent his father boxes of feces.
* ''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 the third 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/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 husband's 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/{{Supernatural}}'':
** In the fourth 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/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/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.
* ''Series/TheVampireDiaries'':
** [[IdenticalGrandson Katherine is Elena's great-great...grandmother.]]
** Alaric, due to his marriage to Isobel is Elena's stepfather.
* ''Series/{{Willow}}'': Scorpia, leader of the [[BanditClan Bone Reavers]], is revealed as Jade's long-lost older sister. Jade previously had believed her entire birth family was dead.
* 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.
* ''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 son, making William the half-brother to Mulder and Jeffrey.]]
*** [[spoiler: At the end of the series, it was revealed that Scully was pregnant again this time with Mulder's child. If she carries to term and gives birth, the child would be William's maternal half-sibling but paternal half-nephew or niece as well as CSM's grandchild.]]
** Scully had a daughter she never knew about thanks to some ova-stealing. [[spoiler:Unfortunately, she only knows her briefly since before her death.]]
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