Ferdinand de la Cerda
Ferdinand de la Cerda (1255–1275), eldest son of Alfonso X of Castile and Violant of Aragon, was heir apparent to the Castilian throne. His name de la Cerda meant “of the bristle”. In 1268 he married Blanche, daughter of Louis IX of France; their two sons, Alfonso and Fernando, began the Infantes de la Cerda line.
He ruled Castile as regent from 1274 while his father pursued the German crown. In 1275 Marinid troops invaded; Ferdinand raised troops and marched south but died at Villa Real. His brother Sancho seized the throne, disinheriting his sons.