Algirdas sibling Kęstutis
Algirdas (Belarusian: Альгерд, Alhierd, Ukrainian: Ольгерд, Ольґерд, Olherd, Olgerd, Polish: Olgierd; c. 1296 – May 1377) was the Grand Duke of Lithuania 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 80 kilometres (50 miles) of Moscow.
brother or sister kin