Siemowit III of Masovia was a prince of Masovia and a co-regent of the lands of Warsaw, Czersk, Rawa, Gostynin and other parts of Masovia. Wikipedia
Born: 1320
Died: June 16, 1381 (age 61 years)
Great grandchildren: Bolesław IV of Warsaw, Siemowit VI of Płock, Frederick III, Holy Roman Emperor, and more
Great-grandparents: Siemowit I of Masovia, Casimir I of Kuyavia, Leo I of Galicia, and more
Grandchildren: Euphemia of Masovia, Siemowit V of Masovia, Władysław I of Płock, and more
Children: Siemowit IV, Duke of Masovia, Janusz I the Old, Henry of Masovia, and more
Parents: Trojden I, Duke of Masovia and Maria of Galicia
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