In 1334, Afonso IV of Portugal invaded the kingdom of Castile and León, entering through the lands of Galicia. However, Pedro Fernandez de Castro refused to fight against him, due to the favors he received in the past at the court of Portugal. Alfonso XI gave him the County of Trastámara, which the sovereign had intended to give his son Henry. Due to his military skills, Alfonso XI sent Pedro Fernandez to fight Muslims in Andalusia, where he fought at the Battle of Salado in 1340, where tradition refers to Pedro Fernandez de Castro grabbed his spurs of gold from the Marinid sultan of Morocco, Abu Al-Hasan Ali ibn Othman.
His second wife was, Isabel Ponce de Leon,[2] daughter of Pedro Ponce de Leon, Lord of Cangas and Tineo, and his wife, Sancha Gil de Braganza. Their children were:
Fernando Ruiz de Castro[3]toda la lealtad de España ("all the loyalty of Spain")(c. 1338 – 1377), Count of Lemos, Sarria and Trastamara, standard-bearer and steward of King Peter of Castile.
Pedro de Castro and Isabel Ponce de León, in a 17th-century Portuguese painting series depicting the ancestors of the Portuguese branch of the Castro family (Ficalho Palace, Serpa, Portugal)
At his death, the body of Pedro Fernandez de Castro was taken to Galicia and buried in the Cathedral of Santiago de Compostela. His remains were buried in the choir of the Cathedral. During 19th century his tomb was examined and found next to his remains were some pieces of silk, a brooch and gold spurs, which are supposedly those of Sultan of MoroccoAbu Al-Hasan Ali ibn Othman, of which Pedro Fernandez de Castro had seized during the Battle of Salado.