There are theories that pretty much everyone in Westeros is a Targaryan, but the most enduring is that the primary heir to that throne is Jon Snow. The idea itself isnt particularly unlikely - George R.R. Martin famously asked David Benioff and D.B. Weiss Who is Jon Snows mother? in order to judge their worthiness to produce the show. He never said whether their guess was correct but Weiss said that his smile was his tell. So who is the most unlikely person to be the mother of Ned Starks bastard son? Naturally the answer (if youre not a Lannister) is his sister, Lyanna. This is because he isnt Neds son at all hes the son of Rhagar Targaryen and was taken by Ned from his dying sister at the Tower of Joy. This is an element not covered in any great detail in the series but the books show Ned travelling to that location in Dorne at the end of Roberts Rebellion. There he finds three Kingsguard defending the Tower (remember this was after the sacking of Kings Landing) and he and his companions fight their way inside where he finds his sister in a pool of blood. Speculation is that this was Jons birth gone wrong and Lyanna made Ned promise before her death that he would protect the boy. As Robert would have killed any potential Targaryan heirs in Westeros, Ned had to hide Jon as his own bastard. Why would the overly honourable Ned Stark ever cheat on his wife? The story of a Stark/Targaryan child would be suitable to be called A Song Of Ice And Fire.
