Catherine Montagu, Countess of Salisbury English countess (1304–1349) Parents Sibylla de Tregoz William de Grandison, 1st Baron Grandison Children Lady Elizabeth Montagu John de Montacute, 1st Baron Montacute Lady Sibyl Montagu Philippa de Montagu William de Montacute, 2nd Earl of Salisbury Siblings Peter de Grandison Mabel de Grandson John Grandison John Grandisson Agnes de Grandson Partners William Montagu, 1st Earl of Salisbury