Isabella of Gloucester and Hertford English noble (1226–1264) Parents Isabel Marshal Gilbert de Clare, 5th Earl of Gloucester Children John de Brus Robert de Brus, 6th Lord of Annandale Siblings Amice de Clare Henry of Almain Richard de Clare, 6th Earl of Gloucester Agnes de Clare Gilbert de Clare Isabella of Cornwall John of Cornwall Nicholas of Cornwall William de Clare Partners Robert de Brus, 5th Lord of Annandale