In what year did Sigismund Casimir's mother die?
Sigismund Casimir Sigismund Casimir, Crown Prince of Poland (Polish: "Zygmunt Kazimierz Waza" ), (1 April 1640 – 9 August 1647) - was the only legitimate son of King Władysław IV and his first wife Queen Cecilia Renata. He was named after his grandfather Sigismund III, and uncle John Casimir.
Catherine I of Russia Catherine I (Russian: Екатери́на I Алексе́евна , "Yekaterina I Alekseyevna" , born Polish: "Marta Helena Skowrońska" , later known as Marta Samuilovna Skavronskaya; 15 April [O.S. 5 April] 1684 – 17 May [O.S. 6 May] 1727 ) was the second wife of Peter the Great and Empress of Russia from 1725 until her death.