Upon the death of the Castilian King Alfonso XI in 1350, his eldest son, Peter, took control of the Castilian throne as Peter I of Castile. Peter was born to Alfonso and his wife, Maria of Portugal, but Alfonso lived out a long and public affair with Eleanor of Guzman. Alfonso's illegitimate children by Eleanor, known collectively as the Trastámaras, immediately became rivals of the newly crowned Peter. Because of a personal history including political murders, his enemies quickly nicknamed him Peter the Cruel. Also increasing the hostilities between Peter and his half brothers was the act of Peter's mother taking the opportunity of his power to have Eleanor of Guzman arrested and executed.