Sancho was the second son of
Alfonso X and
Yolanda, daughter of
James I of Aragon. His elder brother,
Ferdinand de la Cerda, died in November 1275. In 1282 Sancho assembled a coalition of nobles to declare for him against Ferdinand's son
Alfonso, then took control of the kingdom when Alfonso X died in 1284. This was all against the wishes of their father, but Sancho was crowned in
Toledo nevertheless. Sancho's ascension was in part due to his rejection of his father's elitist politics. Sancho was recognised and supported by the majority of the nobility and the cities, but a sizable minority opposed him throughout his reign and worked for the heirs of Ferdinand de la Cerda. One of the leaders of the opposition was his brother
John of Castile, who united to his cause the lord of Biscay, Lope Díaz III de Haro. Sancho responded by executing the Lord of Biscay and incarcerating his brother. According to the chroniclers, he cemented his hold on power by executing 4,000 other followers of Infante Alfonso, son of Ferdinand de la Cerda, in
Badajoz. He executed 400 more in
Talavera and more in
Ávila and Toledo. Upon dispensing with this opposition, Sancho pardoned his brother, who was released. John bided his time before fomenting revolt again: the conflict over
Tarifa. He called in the aid of the
Marinids in Morocco and besieged
Guzmán the Good in his castle (1291). At this siege the innocent son of Guzmán died in what has been considered a famous act of heroism. Tarifa was faithfully defended until Sancho could rescue it and the Marinids retreated to the Maghreb. The intention of both John and the Sultan of Marinids, to invade, was foiled. When
James II succeeded to the
Crown of Aragon, he endeavoured to bind the two crowns more closely and for Christian forces to unite to
reconquer the Iberian peninsula from
Islam. Indeed, both of James' predecessors had tried to do likewise. Sancho was also the friend and tutor of
Juan Manuel of Castile. Just before succumbing to a fatal illness (possibly
tuberculosis) he appointed his wife,
María de Molina, to act as regent for his nine-year-old son, Ferdinand IV. He died on 25 April 1295 in Toledo. ==Family==