Who married Helena?

Casimir of Bytom (Polish: Kazimierz; 1253/57 – 10 March 1312) was a Duke of Opole during 1282–1284 (with his brother as co-ruler) and Duke of Bytom from 1284 until his death.

He was the second son of Władysław, Duke of Opole–Racibórz, by his wife Euphemia, daughter of Władysław Odonic, Duke of Greater Poland.