Sancho III of Navarre
The minority of Count García Sánchez led Castile to accept Sancho III of Navarre, married to the sister of Count García, as feudal overlord. García was assassinated in 1028 while in León to marry the princess Sancha, sister of Bermudo III of León. Sancho III, acting as feudal overlord, appointed his younger son (García's nephew) Ferdinand as Count of Castile, marrying him to his uncle's intended bride, Sancha of León. Following Sancho's death in 1035, Castile returned to the nominal control of León, but Ferdinand, allying himself with his brother García Sánchez III of Navarre, began a war with his brother-in-law Vermudo. At the Battle of Tamarón Vermudo was killed, leaving no surviving heirs. In right of his wife, Ferdinand then assumed the royal title as king of León and Castile, for the first time associating the royal title with the rule of Castile.