Question: Who is the maternal grandfather of John Montagu, 1St Baron Montagu?
Sentence (from "John Montagu, 1st Baron Montagu"): He was the son of William Montagu, 1st Earl of Salisbury by his wife Catherine Grandison, and younger brother of William de Montacute, 2nd Earl of Salisbury (1328–1397).
Relevant evidence: Yes