2. Aegon Targaryen (no, not Jon Snow)
There’s another Aegon Targaryen in the books, one that the show left out entirely: the son of Rhaegar and Elia Martell, and not Lyanna Stark, though there's that "Aegon Targaryen," too, the Jon Snow we know and tolerate. In the books, this Aegon, going around with blue hair and purple eyes as a guy named Griff, claims that the Aegon thought murdered by The Mountain, like the rest of Elia Martell's children, when he was just a baby had actually been swapped with another baby, and Varys snuck the true Aegon out of the castle.
Novel version of Varys has pivoted to this guy, assuming he’s the best option for the Targs to retake the Iron Throne (Varys has been anti-Lannister for a long time). Because of some key passages, a lot of book readers think that this Aegon is a fake, but still, he managed to raise an army (well, he bought the Golden Company) and is assaulting the Stormlands as King’s Landing deals with its forehead carving Faith Militant infestation and the Tyrell power grab. King Tommen -- still alive! -- has declared this Aegon a pretender as well, obviously to keep the throne to himself. But this book Aegon/Griff, claiming to be a descendant of Rhaegar, has as good a chance at the Iron Throne as Jon Snow did in the back half of Season 8 of Game of Thrones: He’s a Targaryen with the "right" genitals.