Sancho was the eldest son of King
Alfonso VII of León and Castile and
Berengaria of Barcelona. He was endowed with the "Kingdom of Nájera" in 1152, and, according to Carolina Carl, never appears in documents as "king of
Nájera". He also succeeded
Urraca the Asturian in ruling the . His father's will partitioned the kingdom between his two sons: Sancho inherited the kingdoms of Castile and Toledo, and
Ferdinand inherited León. The two brothers had just signed a treaty when Sancho suddenly died in the summer of 1158, being buried at Toledo. During his reign, the castle of
Calatrava-la-Vieja was conceded to Abbot Raymond Serrat of
Fitero, who proposed using the lay brothers of his monastery as knights to defend this
castle. These knights would give rise to the
Order of Calatrava, which was confirmed in 1164 by
Pope Alexander III. The
Treaty of Sahagún of May 1158, outlined the spheres of conquests between
Leonese and Castilian against
al-Andalus. A possible division of the
Portuguese kingdom among the two sons of Alfonso VII, would come to nothing due to the premature death of Sancho. ==Marriage==