The next six years of his reign were full of rebellions on the part of the nobles. Early life and reign until majority James was born at Montpellier as the only son of Peter II and Mary, heiress of William VIII of Montpellier and Eudokia Komnene.By the Peace of Alcalá of 31 March 1227, the nobles and the king came to terms. James first married, in 1221, Eleanor, daughter of Alfonso VIII of Castile and Leonora of England. 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.
His long reign saw the expansion of the Crown of Aragon on all sides: into Valencia to the south, Languedoc to the north, and the Balearic Islands to the east.
By a treaty with Louis IX of France, he wrested the Principality of Catalonia from nominal French suzerainty and integrated it into his crown.
Doña Violante de Aragón (1236-1301), mujer de Alfonso X el Sabio.
Doña Constanza (1239-1269), esposa del infante castellano Don Manuel, hermano de Alfonso X el Sabio.
Peter endeavoured to placate the northern crusaders by arranging a marriage between his son James and Simon's daughter. His long reign saw the expansion of the Crown of Aragon on all sides: into Valencia to the south, Languedoc to the north, and the Balearic Islands to the east.