sentences:  He was a Duke of Czersk, Warsaw, Liw, Zakroczym and Nur during 1503-1524 (under regency until 1518) jointly with his brother, and sole ruler during 1524-1526 as the last male member of the Masovian Piasts.He was the second son of Konrad III the Red and his third wife Anna, a daughter of Mikolaj Radziwiłł "the Old", Voivod of Vilnius and the first Grand Chancellor of Lithuania.After the death of their father on 28 October 1503, Janusz III and his younger brother Stanisław inherited his domains, but because they are minors, remained under the regency of their mother.