Question: What is the date of death of John Ii Casimir Vasa's mother?
Answer: 10 July 1631

He was the third and last monarch on the Polish throne from the House of Vasa. Constance of Austria (24 December 1588 – 10 July 1631) was queen of Poland as the second wife of King Sigismund III Vasa and the mother of King John II Casimir.