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.
Margareta of Celje Margareta of Celje (German: "Margareta von Cilly" , Polish: "Małgorzata Cylejska" , Slovene: "Margareta Celjska" ) (1411 – 22 July 1480) was a noblewoman member of the Slovenian House of Celje and by marriage Duchess of both half Głogów and Ścinawa.