Euphemia of Opava 1352 (1319–1352) Parents Anna of Racibórz Nicholas II, Duke of Opava Children Janusz I of Warsaw Siemowit IV Euphemia of Masovia Margaret of Masovia Siblings Margaret of Opava John Hanus Duke of Opava-Ratibor Wenceslaus I of Opava Přemek I, Duke of Opava Nicholas III, Duke of Opava Partners Siemowit III, Duke of Masovia