He was invested as the first Count of Medinaceli in 1368, and he married Doña Isabel de la Cerda in 1370.
Isabel, the widow of Ruy Pérez Ponce de León, was the granddaughter of Alfonso de la Cerda, a grandson of King Alfonso X of Castile.
She was granted large estates on the condition that she relinquish all claims to the Crown of Castile for herself and her heirs.
[1] He chose to stay in Castile when Henry killed King Peter at the Castle of Montiel in March 1369.
[citation needed] The family later had extensive estates in the Spanish provinces of Soria and Guadalajara.