Who married Katharina von Liegnitz?

Frederick Casimir of Cieszyn also known as of Fryštát (Polish: Fryderyk Kazimierz Cieszyński or Frysztacki; German: Friedrich Kasimir von Teschen-Freystadt; b. December 1541/January 1542 - d. 4 May 1571), was a Polish prince member of the House of Piast in the Cieszyn branch and ruler over Fryštát, Skoczów (both since 1560), and Bielsko (since 1565).

He was the second child but only son of Wenceslaus III Adam, Duke of Cieszyn, by his first wife Maria, daughter of John III of Pernstein.