Vladimir Olgerdovich was a son of which ruler of medieval Lithuania?
Algirdas Algirdas (Belarusian: Альгерд , Russian: Ольгерд , Polish: "Olgierd" ;  1296  – May 1377) was a ruler of medieval Lithuania. He ruled the Lithuanians and Ruthenians from 1345 to 1377. With the help of his brother Kęstutis (who defended the western border of the Duchy) he created an empire stretching from the present Baltic states to the Black Sea and to within fifty miles of Moscow.
Michael Žygimantaitis Michael Žygimantaitis (Lithuanian: "Mykolas Žygimantaitis" , Polish: "Michał Bolesław Zygmuntowicz" ; before 1406 – shortly before February 10, 1452 in Moscow) was the last male descendant of Kęstutis, Grand Duke of Lithuania. He supported his father Sigismund Kęstutaitis in power struggles with Švitrigaila. In 1435 he led his father's army to victory in the Battle of Pabaiskas. After his father's assassination in 1440, Michael unsuccessfully fought against Casimir IV Jagiellon for the title of the Grand Duke of Lithuania. At first Michael was supported by Samogitia, but in 1441 Casimir issued a privilege confirming Samogitia's semi-autonomous status and thus avoiding a civil war. Until 1447 he was supported by Dukes of Masovia. In 1448 Michael asked help from the Crimean Khanate. With their help he attacked and shortly took control of Kiev, Starodub, Novhorod-Siversky. Soon he was captured and transported to the Grand Duchy of Moscow where he died under unclear circumstances (possibly poisoned). He was buried in Vilnius Cathedral.