From A Wiki of Ice and Fire
Barristan Selmy, also known as Barristan the Bold, is a celebrated hero in Westeros and a long time knight in the Kingsguard. Barristan was the heir of Lyonel Selmy. As a boy of ten, he donned the armor of a mystery knight during a tourney, where Prince Duncan the Small took pity on him when all those others present laughed at the small boy. Barristan lost at his first tilt, and Prince Duncan named him "the Bold" upon discovering his opponent had been a ten year old boy.
Barristan was knighted at the age of 16 by King Aegon V, and joined the Kingsguard at the age of 23, after slaying Maelys the Monstrous during the War of the Ninepenny Kings during the reign of Jaehaerys II. Barristan continued to serve during the reign of Aerys II, whom he rescued from captivity during the Defiance of Duskendale. Barristan also fought in the Rebellion, where he became wounded on the Trident. Pardonned by King Robert Baratheon, Barristans service as a Kingsguard knight ended when King Joffrey Baratheon declared Barristan too old, and fired him. The events in King's Landing that followed lead Barristan to reevaluate his life as a Kingsguard, and comes to the conclusion that his true monarch is across the Narrow Sea. Barristan eventually finds himself in the service of Queen Daenerys Targaryen.
A renowned tourney knight, Barristan is one of the most respected knights in the Seven Kingdoms. Though an old man, even at the age of 63, Barristan still rides forth into battle. Considering his Kingsguard vows to be important, Barristan has felt nothing but contempt for Jaime Lannister since the Sack of King's Landing. Read more...