Aegon was from the island of Dragonstone, which his family had settled over a century before the Doom of Valyria. According to Targaryen tradition, Aegon married within the family; however, instead of just one sister, he married both of them: his elder sister, Visenya, and his younger sister, Rhaenys. All three were dragon-riders before they were wed. Eventually Aegon decided to go west to Westeros, and for years he planned his conquest of the Seven Kingdoms.

When he was ready, he and his two sister-wives Rhaenys and Visenya, landed with his army on the east coast of Westeros at the mouth of the Blackwater Rush. With the aid of their three dragons (Vhagar, Meraxes, and Balerion the Black Dread) Aegon led the Targaryen army to victory after victory, conquering or subjugating six of the seven kingdoms of the Westeros continent and establishing the Riverlands as a separate region. He failed to conquer Dorne, however, and eventually was forced to respect their autonomy.