You know what plotline would translate well into the Harry Potter-verse? Oedipus Rex. There's a prophecy that he'll kill his dad and marry his mom (or maybe sister), so they curse him and abandon him in the muggle world. His dad...is a Death Eater, maybe? The wizarding world doesn't have the "marry wife of dead king to become the king" thing, though, so that'd have to be fiddled with. Maybe with the marriage law trope?