 They had seven or eight children, including Vytautas the Great.After Algirdas' death in 1377, his son Jogaila became the Grand Duke.At first Kęstutis and his son Vytautas acknowledged Jogaila's rule, but after Jogaila signed the controversial Treaty of Dovydiškės with the Teutonic Knights, Kęstutis seized Vilnius and became the Grand Duke in late 1381.