->'''Forrest:''' You're a mama, Jenny.\\
'''Jenny:''' I'm a mama...his name's Forrest.\\
'''Forrest:''' Like me.\\
'''Jenny:''' I named him after his daddy.\\
'''Forrest:''' He's got a daddy named Forrest too?\\
'''Jenny:''' You're his daddy, Forrest.
-->-- ''Film/ForrestGump''

A man's girlfriend leaves him and marries someone else. She and her new husband have a son together. The man, jealous, develops feelings of resentment and even hatred towards the boy, whom he believes to be the offspring of the woman he loves by another man. [[UnbalancedByRivalsKid When they meet, the relationship between them is tense at best, homicidal at worst.]]

Then one day someone [[TheReveal reveals]] the truth. The man was the child's father all along! He's spent years resenting someone who was in fact his own son!

This is a common variation on the Your Son All Along trope. This trope covers any situation where a man believes that a child is his love-interest's by another man, then discovers that he is in fact the true father. Basically, it's the inverse of cuckolding.

For obvious reasons, the parent in these stories is almost always male. For less obvious reasons, the child is usually male, too. In many cases there is an adversarial relationship between parent and child prior to the revelation, but not always.

Sub-trope of LukeYouAreMyFather and MamasBabyPapasMaybe. The distinguishing feature is that the parent originally believes the child is someone else's, and only discovers the truth later - sometimes not till after the child is dead! This is significant because in most examples of LukeYouAreMyFather, the surprise comes from the man learning that he is a parent, with the potential responsibilities that that entails. In ''this'' trope, the surprise comes from the man learning that he is the parent of a ''particular child''. This forces him to rethink his relationship with that child and also, potentially, with the child's mother.

Expect lots of unmarked spoilers.



* One FandomSpecificPlot for the ''Literature/HarryPotter'' fanfics involves Harry turning out to be Snape's son.

[[folder: Film ]]

* ''Film/IndianaJonesAndTheKingdomOfTheCrystalSkull'' has Indy finding out that Mutt is his son.
* Used hilariously and tragically in the French duology ''Jean de Florette'' and ''Film/ManonDesSources''. In the first film, the protagonist wants the titular Jean to sell him his land, and plays many tricks on him to pursuade him to do so. It doesn't help that Jean is the son of his childhood sweetheart Florette, who left him and married another man while he was away at war. In the end, he successfully drives the Jean to his death and takes the land. In the second film Jean's daughter, Manon, takes revenge for her father's death. It is only at the end of this film that the main character discovers that, contrary to what he thought, Jean was not Florette's son by her husband, but his own son, and that he has unwittingly [[MyGodWhatHaveIDone caused the death of his only child]] and [[HeelRealisation been in conflict with his granddaughter!]]


[[folder: Literature ]]

* ''Literature/TheAmazingAdventuresOfKavalierAndClay'': [[spoiler: Tommy's parentage, while known to the reader, was unknown to Joe until Rosa and Sam revealed the truth.]]
* Inverted in ''The Mayor of Casterbridge''. The title character drunkenly sells his wife and infant daughter to another man. Two decades later, the other man dies and the wife returns to her original husband, bringing her daughter along with her. It is only upon the ''wife'''s death that the protagonist learns that [[spoiler:the daughter is ''not'' the same child he gave up, but a different child fathered by the second husband.]]
* ''Literature/TheThornBirds''. Although in this case, Ralph adored Dane the moment he saw him (only after Dane's death does he admit that deep down, he probably knew all along), and instead harbors some resentment towards his mother Meggie, assuming that despite their passionate interlude (when Dane was conceived), she returned to her neglectful husband Luke.


[[folder: Live-Action T.V. ]]

* Inverted on ''Series/DaysOfOurLives''. Craig is floored when wife Nancy confesses that she had a teenage daughter (Chloe) that she gave up for adoption. He asks her how she could hide the fact that "they" had a child together (they'd been childhood sweethearts but lost touch when he left for college, reuniting years later) and is devastated when she tells him the girl is ''her'' daughter, not his, meaning that she had cheated on him. After a rough start, the three are able to bond as a family. Until the girl becomes ill and needs a bone marrow transplant, at which point Nancy confesses that she's her ChildByRape. However, when the rapist's blood type doesn't match the girl's, Craig realizes that the young woman who he's grown to love as if she were his own daughter. . .''is'' his daughter.
* On ''Series/GeneralHospital'', Alan and Monica spent several years believing that their son AJ was the result of Monica's affair, before finding out that he was Alan's son after all. Unfortunately, crucial bonding time had been lost between the two, resulting in years of AJ being TheUnfavorite (to the son conceived during ''Alan's'' affair) and him being an alcoholic failure. Decades later, AJ (correctly) suspected that he was the father of Carly's unborn child, but she lied and told him that his brother Jason was, fearing that either AJ or her boyfriend Tony would take the child away from her. Years later, Jason's girlfriend Robin finally told AJ the truth.
* ''Series/MyNameIsEarl'': Joy believes that Li'l Chubby is Dodge's father, but she's afraid of him, because she witnessed him mistreating another woman who claimed to be pregnant with his child. Earl wants her to come forward to Chubby, because he can see that Dodge (and Earl Jr.) are suffering due to their living in PerpetualPoverty. Joy tells him to drop it, but he persists, and gets a DaddyDNATest, against all odds (with a little help from Darnell). The test shows that Dodge is ''not'' Li'l Chubby's...but Earl's. It turns out, Earl and Joy conceived him at a Halloween party, and did not recognize each other afterwards. For the six years that they were married, Earl had been led to believe that Dodge's biological father was a stranger from a concert. In another ShockingSwerve, the test also shows that [[ChocolateBaby Earl Jr]]. is ''not'' Darnell's, as previously thought. It's never stated who his father actually is, due to the series being canceled, though WordOfGod says it was supposed to be a celebrity.
* ''Series/ScreamQueens2015'': A DNA test proves that Weston Gardner is the father of Boone and Hester.
* In ''Series/{{Scrubs}}'' when Jordan becomes pregnant the first time she claims that the father was someone she had a one-night stand with, but is unclear which one. It is actually Dr. Cox's baby, but she doesn't tell him in order to hold their [[ItMakesSenseInContext relationship together]]. Eventually it leaks to Dr. Cox that Jack is his son, at which point Dr. Cox is angry at Jordan for keeping it a secret from him.
* In ''Series/{{Dallas}}'', both Sue Ellen and JR believed that her son was the result of an affair with Cliff Barnes, JR's arch-rival. When it's discovered that Cliff might have a hereditary condition that could be passed to offspring, it is found out that John Ross III was, in fact, JR's son.


[[folder: Theatre ]]

* In ''Theatre/LoveNeverDies'', the Phantom realizes at the end of Act One that Gustave is his son, not Raoul's.


[[folder: Video Games ]]

* At the end of ''VideoGame/MetalGearSolid4GunsOfThePatriots'', in a ThrowTheDogABone moment it's reveal that Rose's son is Raiden's (her marriage to Campbell was a sham to prevent the Patriots coming after the kid to get leverage over Raiden). He [[WeaponJr then hammers it in by doing the same moves Raiden does with a toy sword]].


[[folder: Visual Novels ]]

* A rare female version can be found in ''VisualNovel/UminekoWhenTheyCry'' when it's confirmed in Ep 8 that [[spoiler: Battler's biological mother isn't Asumu but Kyrie. A baby switch was made by Rudolf when Asumu's child was a stillbirth and he thought it would be easier since he and Asumu was married while Kyrie was a lover.]]


[[folder: Western Animation]]
* Throughout the first half of ''WesternAnimation/TheVentureBrothers'' Dermott Fictel is assumed to be the illegitimate son of [[TestosteronePoisoning Brock Samson]] ,but in Season 4 it was revealed [[spoiler: he's actually the third Venture brother and [[FamilyRelationshipSwitcheroo his mother isn't even his actual mother, but his grandmother]]]].