Aerys was born to Prince Jaehaerys, the second son of Aegon V. In his youth, he was charming, generous, handsome, resolute, but prone to fits of anger. As he became older, he became increasingly jealous, suspicious and cruel. While still a teenager, Aerys married his sister Rhaella in accordance with the family tradition of dynastic incest. There was no fondness between the two siblings.
Rhaella gave birth to their first son, Rhaegar, during the the tragedy of Summerhall, which killed King Aegon V and his heir, Prince Duncan. Aerys's father Jaehaerys only ruled for three years before passing away, leaving the throne to Aerys.
He ruled with great promise for 12 years, helping the realm recover from the tragedy of Summerhall and filling his court with many young advisors. He appointed Tywin Lannister as Hand of the King, impressed with the way he dealt with the rebellion at Casterly Rock. Aerys came to regret this, as Tywin was a brilliant administrator, and it was whispered that it was the Hand who truly ruled the kingdom, not Aerys himself. Lord Tywin's captain of his household guard, Ilyn Payne, lost his tongue after making such comments. Tywin held a tourney in the king's name, hoping to propose a marriage between his daughter Cersei and Prince Rhaegar. Aerys refused, stating that no servant's daughter was fit to marry a prince. Tywin would not forget that insult. It was also well-known that Aerys lusted after Tywin's wife Joanna, and jested that it was a shame the lord's right had been banished in Westeros. He also agreed to name Tywin's son Jaime as a knight of the Kingsguard, not as an honor, but to deprive Tywin of an heir to Casterly Rock. Rhaegar married the Dornish princess Elia Martell despite Tywin's hopes.
Aerys resolved to handle his own affairs without the aid of his Hand. This proved to be terrible, as Aerys was held captive in Duskendale for several months by a rebellious lord who withheld taxes. It was only after Barristan Selmy infiltrated and rescued the king. In his fury, he immediately ordered the deaths of the lord of Duskendale and his family, extinguishing House Darklyn forever. This event sank Aerys deeper into his madness, refusing to leave the Red Keep for any reason.
The next time Aerys would leave the Keep was to attend the a tourney at Harrenhal at his advisor Varys's urging. It was there that Rhaegar won the tournament and declared Lyanna Stark as his queen of love and beauty. Sometime after, Lyanna was abducted by Prince Rhaegar, setting Robert's Rebellion in motion. Brandon Stark rode to King's Landing with a group of companions, ordering Rhaegar to come out and die. Rhaegar was not present, though, and Aerys ordered Brandon and his friends under arrest for threatening the crown prince. Lord Rickard Stark was ordered to court to answer for his son's crimes, and there both Rickard and Brandon were slowly tortured to death.
Fearful of the rebels winning, Aerys ordered one last act of revenge. He ordered his pyromancers to place caches of wildfire throughout King's Landing, intending to burn the city rather than allow Robert to have it intact. When Tywin Lannister's host was let into the city gates, Aerys ordered Jaime to kill his father and ordered the wildfire caches to be ignited. However, before the plot could be carried out, Jaime slew the King.