James was born at Montpellier as the only son of Peter II of Aragon and Marie of Montpellier, heiress of William VIII of Montpellier and Eudokia Komnene. As a child, James was a pawn in the power politics of Provence, where his father was engaged in struggles helping the Cathar heretics of Albi against the Albigensian Crusaders led by Simon IV de Montfort, Earl of Leicester, who were trying to exterminate them. Peter endeavoured to placate the northern crusaders by arranging a marriage between his son James and Simon's daughter. He entrusted the boy to be educated in Montfort's care in 1211, but was soon forced to take up arms against him, dying at the Battle of Muret on 12 September 1213. Montfort would willingly have used James as a means of extending his own power had not the Aragonese and Catalans appealed to Pope Innocent III, who insisted that Montfort surrender him. James was handed over, at Carcassonne, in May or June 1214, to the papal legate Peter of Benevento. James was then sent to Monzón, where he was entrusted to the care of William of Montreuil, the head of the Knights Templar in Spain and Provence; the regency meanwhile fell to his great uncle Sancho, Count of Roussillon, and his son, the king's cousin, Nuño. The kingdom was given over to confusion until, in 1217, the Templars and some of the more loyal nobles brought the young king to Zaragoza. In 1221, he was married to Eleanor, daughter of Alfonso VIII of Castile and Leonora of England. The next six years of his reign were full of rebellions on the part of the nobles. By the Peace of Alais of 31 March 1227, the nobles and the king came to terms.