Question: When did Blanche Of Portugal (1259–1321)'s mother die?
Sentence (from "Blanche of Portugal (1259–1321)"): Blanche of Portugal (25 February 1259 in Santarém, – 17 April 1321 in Burgos; Branca in Portuguese and Blanca in Spanish), was an "infanta", the firstborn child of King Afonso III of Portugal and his second wife Beatrice of Castile.
Relevant evidence: Yes