King Aegon Targaryen, also known as Young Griff, and self-proclaimed Aegon VI Targaryen, though the succession line of the Iron Throne doesn't recognize this, is the son of Elia Martell and Rhaegar Targaryen. He was supposedly killed by Ser Gregor Clegane during the Sack of King's Landing in Robert's Rebellion, but it is revealed that, supposedly, this was not the case.

Aegon currently leads the Golden Company in an invasion of the Seven Kingdoms, where he has taken several lands in the Stormlands, and plans to lay siege to the Baratheon seat of Storm's End.

Given Aegon's parentage, in actuality, he has a better claim to the Iron Throne than any other character, even Daenerys Targaryen. However, this is all assuming that Aegon is who he claims to be, and not a pretender.