 He made a pilgrimage to Santiago de Compostela in March 1224 . According to the Latin Chronicle of the Kings of Castile , John went to the Kingdom of León to marry one of the elder daughters of Alfonso IX of León ( Sancha or Dulce ) because Alfonso had promised him the kingdom " along with her " . The marriage could jeopardize the claim of Sancha 's and Dulce 's half @-@ brother , Ferdinand III of Castile , to León . To protect her son 's interests , Ferdinand 's mother Berengaria of Castile decided to give her daughter ( Berengaria of León ) to John in marriage . Although modern historians do not unanimously accept the chronicle 's account of John 's plan to marry Sancha or Dulce , they agree that the queen of France ( Blanche of Castile , Berengaria of Castile 's sister ) played an important role in convincing John to marry her niece . The marriage of John and Berengaria of León was celebrated in <unk> in May 1224 . 
