In what year did Sigismund Casimir's mother die?
Cecilia Renata of Austria Archduchess Cecilia Renata of Austria (German: "Cäcilia Renata"; Polish: "Cecylia Renata"; 16 July 1611 – 24 March 1644) was Queen of Poland as consort to the Polish-Lithuanian Commonwealth's King Władysław IV Vasa.
Maria Christina of Habsburg Maria Christierna of Austria (10 November 1574 – 6 April 1621), was a Princess of Transylvania by marriage to Sigismund Báthory, and for a period in 1598 elected sovereign Princess regnant of Transylvania.