Born in King's Landing in 107 AC to King Viserys I and his second wife, Queen Alicent Hightower, and named by his mother after the Conqueror. His father never altered the succession: Rhaenyra had been proclaimed heir in 105 AC and hundreds of lords had sworn to defend her right, and Viserys held to that in life and in his will. Aegon bonded the young Sunfyre at thirteen and in 122 AC wed his sister Helaena after the old Valyrian custom; the twins Jaehaerys and Jaehaera followed within a year, and Maelor in 127 AC. He grew up sullen and idle, given to strongwine and to any serving girl within reach, and convinced that his half-sister's Velaryon sons were Harwin Strong's bastards who had stolen his birthright. Archmaester Gyldayn judged that forcing the two broods together at the same feasts and the same training yard only deepened the hatred between green and black.
When Viserys died in his sleep in 129 AC the green council kept the body in its chamber for seven days while they made ready, and only Lord Lyman Beesbury spoke against them. Ser Criston Cole set the Conqueror's iron-and-ruby crown on Aegon's head in the Dragonpit, girded him with Blackfyre, and made him the sixth Targaryen to sit the Iron Throne. Rhaenyra crowned herself on Dragonstone in answer, and the realm split in two. Daemon's hirelings Blood and Cheese took Aegon's heir Jaehaerys in the Tower of the Hand and struck off his head; the king hanged every ratcatcher in the city, and thereafter slept apart from his queen. At Rook's Rest he and Aemond brought down Rhaenys Targaryen and Meleys, but Sunfyre was maimed and Aegon was burned across half his body, his hip and ribs broken and his armour melted into his left arm. He lay a year under milk of the poppy, sleeping nine hours in ten, while Aemond ruled as regent in his place.
When Rhaenyra's dragons appeared over King's Landing in 130 AC, Larys Strong smuggled the king out of the city on a fishing boat. Aegon took Dragonstone back by treachery, shattered both legs leaping from Sunfyre's back in the sky duel with Baela and Moondancer, and fed his sister to his dying dragon while her son Aegon the Younger was made to watch. He came home to a capital whose Iron Throne he could no longer climb, giving judgement instead from a cushioned wooden seat with a blanket over his twisted legs, refusing the poppy and drowning the pain in sweet Arbor red. With the Lads, the Valemen, and Cregan Stark's northmen all closing on the city in 131 AC, Lord Corlys Velaryon counselled abdication and the Wall; Aegon refused, and ordered his nephew's ear cut off and sent to Riverrun. He was found dead in his litter on the way to the royal sept, blood on his lips, poisoned by his own lords. Grand Maester Kaeth set him in the Lives of Four Kings beside Aenys the weakling and Maegor the Cruel, and called him grasping.