As far as Jon knows, he's Ned Stark's bastard son. But there's speculation that Ned lied about Jon's ancestry and he's actually the son of Ned's sister, Lyanna Stark, and Westeros' former king, Rhaegar Targaryan.
Game of Thrones' biggest unsolved mysteries
So what did George R.R. Martin and the cast have to say about this theory? Find out in the video below!