He was engaged in a decades-long fight for control over the Lordship of Biscay with Diego López V de Haro, the uncle of his wife.

He was born before 15 April 1262[1][2] in Seville, the son of Alfonso X, King of Castile and León and Queen Violant of Aragon.

[4] In 1312, after the death of Ferdinand IV, he was appointed guardian of his son Alfonso XI,[5] whom he served alongside Queen María de Molina and Infante Peter of Castile, Lord of Cameros.

He died in 1319 at Pinos Puente, in the battle of Sierra Elvira, also known as the disaster of Vega de Granada.

[3] On 17 February 1281, he married Margaret, who died in 1286, daughter of William VII, Marquess of Montferrat and Elizabeth of Gloucester,[3] with whom he had: One year after the death of his first wife and before 11 May 1287 he married María Díaz de Haro[5][7][3] with whom he had three children: