Answer
Hildegard was the mother of Louis the Pious. Louis was born in 778 AD and was the only son of Charlemagne and Hildegard. He became the King of Aquitaine in 781 AD and inherited the Frankish Empire upon Charlemagne's death in 814 AD. Louis's reign was marked by internal conflicts and external threats, and he is best known for his efforts to divide the Frankish Empire among his sons.