Sancho IV of Castile called the Brave, was the king of Castile, León and Galicia from 1284 to his death. Following his brother Ferdinand's death, he gained the support of nobles that declared him king instead of Ferdinand's son Alfonso. Faced with revolts throughout his reign, before he died he made his wife regent for his son Ferdinand IV.

Ferdinand de la Cerda was the heir apparent to the Crown of Castile as the eldest son of Alfonso X and Violant of Aragon. His nickname, de la Cerda, means "of the bristle" in Spanish. There are various accounts of the origin of this name, including that it was a reference to being born with a full head of hair or that he was born with a hairy mole, resembling a bristle or mane, on his chest or back according to different accounts.