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.
Vladislaus II of Hungary Vladislaus II, also known as Vladislav II, Władysław II or Wladislas II (1 March 1456 – 13 March 1516; ; Hungarian: "II. Ulászló" ; Polish: "Władysław II Jagiellończyk" ; Croatian: "Vladislav II. Jagelović" ; Slovak: "Vladislav II. Jagelovský" ), was King of Bohemia from 1471 to 1516, and King of Hungary and Croatia from 1490 to 1516. As the eldest son of Casimir IV Jagiellon, he was expected to inherit Poland and Lithuania. George of Poděbrady, the Hussite ruler of Bohemia, offered to make Vladislaus his heir in 1468. Poděbrady needed Casimir IV's support against the rebellious Catholic noblemen and their ally, Matthias Corvinus, king of Hungary. The Diet of Bohemia elected Vladislaus king after Poděbrady's death, but he could only rule Bohemia proper, because Matthias (whom the Catholic nobles had elected king) occupied Moravia, Silesia and Lusatia. Vladislaus tried to reconquer the three provinces with his father's assistance, but Matthias repelled them.