Sigismund was most likely born in Novhorod-Siverskyi to Dymitr Korybut, son of Algirdas, Grand Duke of Lithuania, and Anastasia, daughter of Grand Prince Oleg of Ryazan, and raised in the court of his uncle Jogaila (Władysław Jagiełło) in Kraków since 1404. Sigismund was rumored to be expected to become his successor on the Polish throne. Being just an adolescent, he commanded his own banner of the Army of the Crown in the victorious Battle of Grunwald in 1410. His elder sister, Olena (Helena) had been married to an important magnate of Bohemian kingdom, duke Jan of Opava and Ratiborz.