Eldest of Queen Cersei's children, born at King's Landing in 286 AC and proclaimed the trueborn son of King Robert Baratheon, though in truth the get of the queen's twin, Ser Jaime Lannister, his fair hair and green eyes the open secret of the court. As a boy of nine or ten he cut open a pregnant she-cat with a dagger to show his father the kittens within, and Robert struck him so hard he lost two milk teeth, an early measure of the prince and the king alike. In 298 AC Lord Eddard Stark was named Hand and Joffrey was betrothed to his eldest daughter Sansa, who rode south with him on the kingsroad in a fever of songs and red roses. On the Trident the prince came upon the butcher's boy Mycah at swords with Arya Stark, drew Lion's Tooth, and cut the boy's cheek before Arya's wolf Nymeria set on him and a tossed sword sent his blade into the river; in recompense Queen Cersei demanded a wolf's life, and since Nymeria was fled Lord Eddard himself put down Sansa's gentle Lady at the holdfast of Darry, while Sandor Clegane ran Mycah down on the kingsroad and brought back the corpse in halves.
When King Robert was gored by a boar in the kingswood and died at the Red Keep, Joffrey was crowned of an age of twelve before the Iron Throne, Cersei regent and Lord Tywin Lannister Hand in absentia. Promised his bride that he would show mercy, he had Lord Eddard taken from the steps of the Great Sept of Baelor by Ser Ilyn Payne's greatsword Ice, and from that day Sansa was a hostage in silks; whenever word came that her brother Robb had won another field in the riverlands, the king sent his Kingsguard to beat her bloody beneath her gown, the white cloaks of Ser Meryn Trant and Ser Boros Blount made the rod of his spite. At the Blackwater, when Stannis Baratheon's fleet broke upon Tyrion Lannister's wildfire and the city walls were stormed, Joffrey carried a fine crossbow he called the Hand's Mercy and shouldered his way back inside the Red Keep to shelter with his mother in Maegor's Holdfast, leaving the defense of the gate to his uncle the Imp.
With the Tyrell host arrived in time to save the throne, his betrothal to Sansa was set aside and a new match was struck with Lady Margaery, the comely widow of Renly Baratheon; the wedding was held in 300 AC at the Great Sept of Baelor and was followed by a feast of seventy-seven courses in the throne room. At the breaking of the pie the boy king took a cup of Arbor gold, choked upon it, and died purple-faced in his mother's arms with the strangler crystal melted from the hairnet of the Queen of Thorns, Lady Olenna Tyrell, who had conspired with Petyr Baelish to spare her granddaughter the marriage bed of a monster. Tyrion was seized for the crime he had not done, and the king's death was thereafter called the Purple Wedding.