Isabel Ferrers Peerage person ID=41670 (b. 1218) Parents Sibyl Marshal William de Ferrers, 5th Earl of Derby Children William de Mohun Isabel de Mohun Siblings Alianore de Ferrers Joan de Ferrers Agnes Ferrers Maud Ferrers Agatha Ferrers Sibyl de Ferrers Elizabeth Ferrers Robert de Ferrers, 6th Earl of Derby William Ferrers Agnes de Ferrers Joan de Ferrers Partners Reginald de Mohun Gilbert Basset