This is when a child, raised as an orphan, turns out to actually be the "next heir to the throne
." It may not be exactly that... But it's something along those lines. There are a multitude of plots that could stem from this trope: The parents could have sent him away so he could have a "normal" childhood, the orphan could be well aware of his royal status, but just needs a way to get it back. The orphan could suddenly be thrusted into the big chair that is the monarch. So there are a lot of possibilities when it comes to orphan monarchs. If the villain is all like, "I will kill the king and his descendants so I can take the throne." Then the orphan can be on the run from the villain trying to kill him... Or he could be the overlooked heir that the villain didn't realize was a rightful heir to the throne. The orphan could BE the villain, obsessed with getting the life he deserves to have, being the true heir an all...
Suddenly Suitable Suitor
is a common plot twist.
Compare Really Royalty Reveal
, Hidden Backup Prince
, Man in the Iron Mask
and Rightful King Returns
- Shasta, from C. S. Lewis's The Horse and His Boy is one. He was abducted by an Evil Chancellor, lost in the middle of a naval battle between the Chancellor's forces and the royal navy, and then was taken in by a fisherman. Later he finds his true family and grows into Cor, King of Archenland.
- Jenna from Septimus Heap, even though her father is alive, but virtually nonexistent.
- Discworld: Captain Carrot Ironfoundersson was orphaned as an infant, then raised by dwarves, before eventually travelling to Ankh-Morpork to become a city guard. He turned out in face to be the rightful 'eir to the throne, and from all appearances he'd be damned good at it, what with his essential king-ness meaning the entire city, horrible selfish jerks to a human, actually like him. But he really doesn't want to be king, and the man in charge doesn't want a king, and Sam Vimes, his boss really doesn't want kings. So he isn't the king, and everyone is happy. Well, everyone within reason.
- Slackjaw from Dishonored. He was raised by a whore and the heart reveals that he is actually a prince, but that he'll never know.