When did the cousin of the Grand Duke of Lithuania die?
Vytautas Vytautas (c. 1350 – October 27, 1430), also known as Vytautas the Great (Lithuanian: "   ", Belarusian: "Вітаўт Кейстутавіч (Vitaŭt Kiejstutavič)" , Polish: "Witold Kiejstutowicz" , Rusyn: "Vitovt", Latin: "Alexander Vitoldus") from the 15th century onwards, was a ruler of the Grand Duchy of Lithuania, which chiefly encompassed the Lithuanians and Ruthenians. He was also the Prince of Hrodna (1370–1382), Prince of Lutsk (1387~1389), and the postulated king of the Hussites.
Morta Morta (died c. 1263) was wife of Mindaugas, the first known ruler of the Grand Duchy of Lithuania. She was the Grand Duchess of Lithuania (until 1253) and later Queen consort of Lithuania (1253–1262). Very little is known about her life. Probably, Morta was Mindaugas' second wife as Vaišvilkas, the eldest son of Mindaugas, was already a mature man active in international politics when Morta's sons were still young and dependent on the parents. After her death, Mindaugas married her sister, the wife of Daumantas. In revenge, Daumantas allied with Treniota and assassinated Mindaugas and two of Morta's sons in 1263.