Сигизмунд Кейстутович
First mentioned in 1413, Jonas Goštautas served as a marshal during the late reign of Vytautas the Great. Following death of Vytautas he continued his duties under Švitrigaila and sided with him against Vytautas' brother Sigismund Kęstutaitis. In 1431 while defending Lutsk from the Sigismund Kęstutaitis' Polish-Lithuanian assault he was captured and imprisoned.