So you have a setting with a monarchy, or where heredity is somehow important (say Superpowerful Genetics are in effect), and the entire royal / superpowered family (or both) are under constant threat of being killed in a surprise attack by their enemies. Sure they'll fail 99% of the time, and most royal families have a Spare to the Throne to ensure there's a backup to inherit, but what to do in case they somehow wipe out everyone in line to inherit (who isn't evil)? Evil Only Has to Win Once after all. The solution is to raise one of the King's children as a commoner far away, without knowledge of their Secret Legacy. The idea being that they'll be safe in anonymity, and they may even be able to be trained or schooled in a way that spares them from becoming snobby and brings them closer to commoners. The kid may be a bastard child, a twin, or the royal family may actually pretend they died in childbirth. In the first case, the Hidden Backup Prince may be a side effect of covering up their father's indiscretions, and the "backup" part is entirely unintentional. Of course, if the Hidden Backup Prince is resentful and finds out about their heritage they may decide to be the cause that wipes out the royal family. Nothing like going from Riches to Rags to motivate spite. Usually though, the Hidden Backup Prince will know nothing of their heritage yet somehow get involved in the plot regardless. See also Rags to Royalty. For the sake of keeping things simple, this trope will cover both intentionally and unintentionally creating a Hidden Backup Prince. Cases such as involuntary separation (through chance or enemy schemes) count. This trope can also be in play even if the royal family isn't killed off-- the Hidden Backup Prince exists as a fail safe, regardless of if it's called into use by the plot.
Examples:Anime and Manga
- In GoLion, the royal family of Altia is killed, save for Princess Fala, who was taken away when the planet was attacked.
- The short-lived manga Barrage: It's revealed towards the end that Astro was the real prince all along; he was stolen shortly after birth and replaced with a "dark matter duplicate" so that he could be raised away from the corruption of the court.
- In King Ralph after the entire British Royal Family is wiped out in a photography accident Ralph is found working as a lounge singer in Las Vegas and recruited to be the new King of England. He didn't know he was related to the monarchy at all - he's a royal bastard, his grandfather having been a Duke and his grandmother a hotel maid.
- Princess Leia in Star Wars. It's a bit of a twist from the normal set up, but she and her brother Luke are being hidden from forces meaning them ill (though it's unusual for this trope that it be their own father). Which at least in her instance is especially ironic since she was a commoner and hidden by posing as royalty.
- Disney's The Man in the Iron Mask has the King's identical twin hidden in a cottage by their father to avoid a power struggle. Of course, the king being a jerk means as soon as he finds out he has a brother who might potentially try to usurp him he goes all out and has him jailed and put in the titular iron mask.
- This is the Backstory for both main character's in Uwe Boll's In the Name of the King films.
- Sleeping Beauty skips the "backup" part and out and out hides Aurora for her protection from Maleficent.
- In Wyrd Sisters, the king's infant son, Tomjon, is hidden away to protect him from his murderous relatives. Unbeknownst to everyone, there's a second son already there - Verence the fool. Though Nanny realizes at the end of the book that neither is the king's son; they're both children of Verence's father, the previous fool.
- Mia Thermopolis from The Princess Diaries was the illegitimate daughter of the Prince of Genovia. Since the Prince was unable to have anymore children due to his cancer treatment, he was forced to reveal to Mia that she is his only heir to the Genovian throne.
- The first Prince Geran from the Belgariad prequels was hidden away only after the rest of his family got butchered.
- In Split Heirs by Lawrence Watt-Evans and Esther Friesner, the King's people believe that twins are a sign of infidelity, so when Queen Artemisia gives birth to triplets, she gives two of them to a nurse who gives them to two other families to raise as commoners. The rest of the book is a hilarious deconstruction of Prince and Pauper tropes.
- In Andre Norton's The Prince Command, Michael was raised in America in total ignorance of his birth. Only when his grandfather and cousin died does he learn he was the rightful heir. (To be sure, this was the consequence of his father running away and marrying in America.)
- In the King Arthur mythos Arthur doesn't know he's the heir to the throne, everyone thinks he's a foundling that Sir Ector took pity on; but Merlin trains him in such a way that he ends up a wise and humble king - unlike he presumably would have been if he had grown up as a prince. Arthur doesn't learn of his true parentage until after Uther, his father, dies and he pulls the sword from the stone.
- In William Shakespeare's Cymbeline: King Cymeline's sons were kidnapped at a young age by a resentful retainer, and grew up thinking the retainer is their father. At the end of the play they're reunited with their real father.
- Animaniacs: Yakko is appointed King of Anvilania this way, as he explains in song.
Yakko: I'm the cousin to the sister / Of son's niece's brother / Of the uncle's daughter's father / Of the nephew's sister's mother / And my grandpa's only cousin / Was the King's daughter's sibling, / But they're all gone,Crowd: So that is whyYakko: I am now your king!
- Larsa Solidor from Final Fantasy XII. He hid himself from his brother (instead of the other way around), but his lineage turned out to be useful in the end when he was needed to take over the Archadian Empire.
- Martin in Oblivion is the illegitimate son of the Emperor, who he gave away to a priesthood. When the Emperor and his legitmate sons are murdered by a cult he's the only one of them left, (which is important, since someone of the Septim line is needed to foil the villains' Evil Plan). Given that his line have a habit of seeing the future, it's possible that he invoked this trope.
- Princess Elincia of Fire Emblem Tellius was brought up in secret this way, ready to assume the throne should everyone else die.
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