It turns out Game of Thrones author George R.R. Martin gave a hint about Jon Snow's parents way back in 2002. Martin was doing an AMA (ask me anything) with fans of the books on Reddit (which was then a little-known online forum). This was three years before the third book had been released, and almost a decade before the A Song of Ice and Fire novels became an HBO series. Back then, only a few dedicated nerds had any theories regarding Jon Snow's lineage. As always, spoilers for the books and TV series lie ahead.
A fan asked Martin a simple and seemingly unimportant question to regarding how characters received their names when their mothers died during or after childbirth:
Since all of their mothers died, who gave Jon Snow, Daenerys Targaryen, and Tyrion Lannister their names?
Fair question. Here's Martin's clever response, with a big old clue dropped in there if you read it carefully:
Mothers can name a child before birth, or during, or after, even while they are dying. Dany was most likely named by her mother, Tyrion by his Father, Jon by Ned.
Very clever Mr. Martin, very clever indeed. Way back in 2002, he implied that Ned was not Jon's father, which has now been confirmed. This means that fans of the books with lots of time on their hands are now scouring Reddit for any more clues about future plot points.