23rd Oct: It's time for the second TV Tropes Halloween Avatar Contest, theme: cute monsters! Details and voting here.
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.