Albert V
Albert V was the son of Albert III, Duke of Mecklenburg, and Agnes (II) of Brunswick-Lüneburg, daughter of Duke Magnus II, Duke of Brunswick-Lüneburg. Albert III died in 1412 and, in accordance with an agreement with John IV, Agnes acted as guardian and regent for Albert V. In 1415 or 1416 he started ruling for himself. After John IV died in 1422, Albert V and John IV's widow acted as co-regents for her minor sons Henry IV and John V.