He was a son of Alfonso X of Castile and Violant of Aragon who was also called Yolanda or Yolante.

He was Lord (señor) of Ledesma, Alba de Tormes, Salvatierra, Miranda del Castañar, Galisteo and Granadilla.

He received from his father the command of the Christian troops during the failed Siege of Algeciras (1278–79).

When his eldest brother, Crown Prince Ferdinand de la Cerda, died before his father, Peter supported his brother Sancho IV of Castile, against the wishes of his father, who had appointed Ferdinand's son Alfonso de la Cerda as his successor.

This biography of a member of the Spanish royal house is a stub.