Maekar I Targaryen, King of the Seven Kingdoms

From Asoiaf

Maekar I of House Targaryen, King of the Seven Kingdoms (reigned 221 Al - 233 AL), was the fourth son of Daeron II Targaryen, King of the Seven Kingdoms and Queen Myriah of House Martell.

He succeeded his older brother Aerys I on the throne.

On his death his fourth son Aegon V became king.