Sancho III of Castile

Sancho III of Castile (1134 – 31 August 1158) was King of Castile and Toledo for one year, from 1157 to 1158. During the Reconquista, in which he took an active part, he founded the Order of Calatrava. He was called el Deseado (the Desired) due to his position as the first child of his parents, born after eight years of childless marriage.

He was the eldest son of King
Alfonso VII of León and Castile and Berenguela of Barcelona. During his father's reign, he appears as "king of Nájera" as early as 1149. His father's will partitioned the kingdom between his two sons: Sancho inherited the kingdoms of Castile and Toledo, and Fernando inherited Leon. The two brothers had just signed a treaty when Sancho suddenly died in the summer of 1158, being buried at Toledo.

He had married in 1151 to
Blanca of Navarre, daughter of García Ramírez of Navarre, having two sons;
Alfonso VIII of Castile, his successor
infante García, who died at birth in 1156, apparently also resulting in the death of Blanca.

There may also have been an older son who died in infancy.