A Dance with Dragons

[The Man]

Ok maybe I've gone crazy, maybe I've become Serapy but I have a small theory of something which we may never know the answer to.

Jon's parentage, throughout the series so far we're led to believe he is Ned's bastard but thinking bout it, Ned went to war with Robert and came back with Jon but will not speak much about his birth or his mother as far as we're aware she was a wet nurse named Wylla.

However there was another possibility what I thought of: Robert Baratheon was meant to marry Ned's sister, Ned's sister never survived the war that made Robert King of the Seven Kingdoms. Considering he was never married to Ned's sister is it possible that Jon was really Robert and Ned's Sisters (sorry can't remember her name now) first born son and in effect the true heir to the Iron Throne (if you count Dany/Viserys out ofcourse) or have I gone crazy thoughts?

I'm honestly amazed you hadn't encountered the theory about Lyanna being Jon's mother before. It's actually more commonly held among fans than the cover story that Jon really is Ned's bastard. However, Rhaegar is usually theorised as his father, with the reasoning that if he were Rhaegar's son then Robert would probably want him dead; thus, hiding him as Ned's bastard would protect him from harm. It would also explain Ned's otherwise unexplained promise to Lyanna which he keeps dwelling upon. Lyanna and Rhaegar are generally accepted to have genuinely been in love, although this is not universally agreed upon either.

There's more explanation here