Aegon V Targaryen, the fifth of his name and remembered as Aegon the Unlikely, was born in 200 AC, the fourth son of Prince Maekar and Lady Dyanna Dayne, and a fourth-born of a fourth-born who had no reason ever to expect a crown. As a boy he was known simply as Egg, and for years he wandered the roads of Westeros as squire to the hedge knight Ser Duncan the Tall, sleeping in ditches and barns and seeing with his own eyes how the smallfolk lived and suffered under their lords. That schooling marked him for life. When his father King Maekar died in 233 AC and the succession fell into doubt, a Great Council was summoned to King's Landing; it set aside the mad Aerion's infant son Maegor, the simple girl Vaella, and Egg's own elder brother Aemon, who had taken a maester's vows and refused the throne, and chose Egg instead, the unlikeliest of Maekar's sons.
For love rather than alliance he wed Betha Blackwood, called Black Betha, and he raised his old master Ser Duncan the Tall to Lord Commander of his Kingsguard. Mindful always of the common people among whom he had lived, Aegon labored to reform the laws of the realm, to grant the smallfolk new rights and protections and to curb the power of the great lords, and for this the lords resented and resisted him bitterly, some near to open revolt. He let his own children follow their hearts in marriage as he had: when his heir, Prince Duncan, set aside his betrothal to wed the lowborn Jenny of Oldstones and was thereafter called the Prince of Dragonflies, the broken pact stirred fresh strife, mended only in part when Aegon's daughter Rhaelle was given to House Baratheon.
Thwarted again and again by his lords, Aegon grew ever more drawn to old prophecies and to the dream of restoring the dragons that might let a king rule without leave of his bannermen. In 259 AC he gathered his kin and his closest friends at Summerhall, the castle of his birth, in a great effort to wake dragons from stone. Whatever sorcery was attempted there ended in catastrophe: a terrible fire swept the halls and consumed the king, his heir Prince Duncan, and the faithful Ser Duncan the Tall, on the very night his grandson Rhaegar was born amid the smoke and ruin. The tragedy of Summerhall passed into song, and the throne passed to Aegon's son Jaehaerys II.