So, in light of recent events in GoT I think we can confirm that Jon Snow is one head of the dragon (in both books and show) and we know that Daenerys is the another one. We don't know with certainty when this will come up, but we can assume that the three heads of the dragon will have some importance in the War for the Dawn, they'll most probably be the three dragonriders. Here is a list of potential candidates for the 3rd head: - Aegon VI Targaryen: the most obvious one, but he's probably