Fedir inherited Navahrudak Castle from his father. After Grand Duchy of Lithuania gained Podolia as a result of the decisive victory against the Golden Horde at the Battle of Blue Waters in 1362, he with his three brothers were appointed by Grand Duke Algirdas to administrate the region. After the last of his brothers died circa 1389, he remained the sole administrator of Podolia for three years until his exile by the Grand Duke Vytautas the Great.