The young Targaryen claimant raised as “Young Griff” is Aegon Targaryen. In A Dance with Dragons, the boy claims to be Prince Aegon, the son of Rhaegar Targaryen and Elia Martell, who was believed to have been killed during the fall of King’s Landing.
Varys claims that the infant Aegon was secretly exchanged for a lowborn child before Gregor Clegane captured the city. The surviving child was smuggled across the narrow sea and eventually raised under the name Young Griff by Jon Connington, a close friend of Rhaegar. The plan is for him to become a Targaryen claimant capable of winning support in Westeros.
The novels deliberately leave his identity uncertain. Some characters and readers suspect Young Griff is an impostor, while others accept the possibility that he really is Aegon. That unresolved question does not make the quiz answer ambiguous: “Aegon Targaryen” is the character’s claimed identity and the canonical name associated with Young Griff.