HBO released an infographic showing multiple connections between major Game of Thrones characters. It's a tale of ice and fire, sex and violence, bastards and kings. Even for viewers and readers of the books, it's quite a visual undertaking to look at all the connections. Warning: spoilers for lots of characters in the entire series ahead.
Here's the entire chart in all its tangled glory. It shows all the genetic connections, marriages, alliances, and many murders as they relate to Ned's promise to watch over Jon Snow:
Here's a closer look at half of the graph:
That black line confirms that Lyanna Stark is Jon Snow's mother. And only she has that big ole' purple dashed line for being supposedly abducted by Rhaegar Targaryen. Then there's the all important, black line between Rhaegar Targaryen and Jon Snow, pointing out Jon Snow's father with all the authority Reddit theories have lacked for years.
As an aside, because this infographic illustrates the history behind Jon's lineage, it is notably missing Cersei Lannister (then we would get to see a black line from both her and Jamie to their three golden-haired children). Tee-hee.
The second half shows that very important red line between Lyanna Stark and Robert Baratheon, because of their engagement. Rheaegar got in the way of that, just a little bit.
So now we know for certain that Jon Snow is a child of ice and fire (Stark and Targaryen). But is he the promised prince? Everyone will have to wait for the books and TV series to answer that burning (and freezing) question.