Question: Who is Hildegard (Abbess)'s paternal grandfather?
Sentence (from "Louis the German"): Grandson of emperor Charlemagne and the third son of Louis the Pious, emperor of Francia, and his first wife, Ermengarde of Hesbaye, he received the appellation "Germanicus" shortly after his death in recognition of Magna Germania of the Roman Empire, reflecting the Carolingian's assertions that they were the rightful descendants of the Roman Empire.
Relevant evidence: Yes