Daeron II Targaryen, the second of his name and remembered as Daeron the Good, was born in 153 AC, the first child of King Aegon IV and his sister-wife Queen Naerys. By every official accounting he was Aegon's trueborn heir, yet whispers followed him all his life that his true father was his uncle Aemon the Dragonknight, Naerys's devoted brother, for the gentle, bookish Daeron was everything his gluttonous, martial father was not. Small and slender and no warrior, he loved books, histories, and the company of maesters and septons, and Aegon scorned him for it; the rift between father and son widened through Aegon's reign, the more so when the king lavished honors on his bastards and gave the sword Blackfyre to Daemon rather than to Daeron. When Aegon died in 184 AC, he left his heir a realm poisoned by his unworthiness and, with his deathbed legitimization of all his bastards, the seeds of the wars to come.
Where his namesake Daeron the Young Dragon had failed to hold Dorne by the sword, Daeron II won it by marriage and treaty. Betrothed in youth to Princess Myriah Martell, he completed the great pact upon his accession: his sister Daenerys was wed to Prince Maron Martell, and Dorne entered the Seven Kingdoms at last, keeping its own laws, its Prince's title, and much of its independence. His reign was peaceful, learned, and just, and he surrounded himself with able men and ruled with a wisdom that earned him his byname. But the Dornishmen he raised to favor at court bred resentment among the lords of the Reach and the stormlands, and his enemies fixed their hopes on his half-brother, the famed warrior Daemon Blackfyre.
In 196 AC that resentment burst into the First Blackfyre Rebellion, when Daemon declared himself the rightful king. Daeron held to his throne as the trueborn line, and his loyalists broke the rebels at the Battle of the Redgrass Field, where his half-brother Brynden Rivers and the longbowmen of the Raven's Teeth shot down Daemon and his twin sons, and his own son and heir, Prince Baelor Breakspear, came up with a Dornish and stormlands host to shatter the rebel rear. With the black dragon thrown down, Daeron showed mercy to the defeated, though against his clemency his counselors warned that pardons would only stoke the next rebellion. He maintained the incomes his father had bestowed upon the Great Bastards, and in the long peace that followed leaned on his heir Baelor as Hand of the King and his other sons, Aerys, Rhaegel, and Maekar.
The good king's house was undone in a single year. In 209 AC Prince Baelor Breakspear died of injuries taken at the Trial of Seven at Ashford, and that same year the Great Spring Sickness swept through King's Landing and carried off King Daeron himself, along with his grandsons Valarr and Matarys, Baelor's sons, within days of one another. With his heir and that branch of his line dead, the crown passed to Daeron's second son, who took the throne as Aerys I.