Siemowit IV, Duke of Masovia
Siemowit IV, also known as Siemowit IV the Younger, was a Polish prince, member of the Masovian branch of the House of Piast and from 1373 or 1374 Duke of Rawa, and after the division of the paternal ... Wikipedia
Born: 1352
Died: 1426 (age 74 years), Gostynin, Poland
Grandchildren: Siemowit VI of Płock, Frederick III, Holy Roman Emperor, Albert VI, Archduke of Austria, and more
Children: Siemowit V of Masovia, Euphemia of Masovia, Cymburgis of Masovia, and more
Parents: Siemowit III, Duke of Masovia and Euphemia of Opava
Spouse: Alexandra of Lithuania (m. 1387)