Sancha, heiress of León

The eldest child and daughter of Alfonso IX of León by his first wife, Teresa of Portugal, Sancha was made co-heiress following the death of one of her younger brothers and the accession to the throne of Castile of the other.

[3] Alfonso also attempted to secure his eldest daughter's rights by marrying her to John of Brienne, the former King of Jerusalem, but his wife Berengaria blocked this action in order to advance her son.

[1] After this fiasco, Alfonso declared Sancha and Dulce his heirs, but upon his death on 24 September 1230, the people of León, who had pledged for Ferdinand in 1206, refused to recognise his daughters, and they in turn ceded their rights to his kingdom to their half-brother on 11 December 1230.

This agreement, negotiated at Valencia de Don Juan by Berengaria and Theresa, with Sancha and Dulce present, is known as the "pact of the mothers".

After the renunciation, Sancha retired to the Cistercian monastery of Santa María in Villabuena, in El Bierzo, which had been founded by her mother, with her father's blessing.