Question: Who is Blanche Of Lancaster's paternal grandfather?
Sentence (from "Henry of Grosmont, 1st Duke of Lancaster"): The son and heir of Henry, 3rd Earl of Lancaster, and Maud Chaworth, he became one of King Edward III's most trusted captains in the early phases of the Hundred Years' War and distinguished himself with victory in the Battle of Auberoche.
Relevant evidence: Yes