His sister, Isabella de Forz, widow of William de Forz, 4th Earl of Albemarle, became Countess of Devon suo jure. Her children predeceased her and she had no grandchildren. Her lands were inherited by her second cousin once removed, Hugh de Courtenay (1276–1340), feudal baron of Okehampton, the great-grandson of Mary de Redvers and Robert de Courtenay (d.1242) of Okehampton. 
The Countess of Halifax also has a daughter from her first marriage with Richard Eustace Parker Bowles: Emma Parker Bowles (born 1974). The Earl and Countess of Halifax live on the 20,000 acre family estate Garrowby Hall near Garrowby, East Riding of Yorkshire. Lady Halifax is the national president of Macmillan Cancer Support.