Mary Stanley, Lady Derby English political hostess (1824–1900) Parents Elizabeth Sackville-West, Countess De La Warr George Sackville-West, 5th Earl De La Warr Children Lord Lionel Gascoyne-Cecil Lord Arthur Gascoyne-Cecil Lady Margaret Gascoyne-Cecil Lord Sackville Gascoyne-Cecil Mary Arabella Stewart, Countess of Galloway Siblings Reginald Sackville, 7th Earl De La Warr Lionel Sackville-West, 2nd Baron Sackville Elizabeth Russell, Duchess of Bedford William Sackville-West Charles Sackville-West, 6th Earl De La Warr Lady Arabella Sackville-West George West, Viscount Cantelupe Mortimer Sackville-West, 1st Baron Sackville Partners James Gascoyne-Cecil, 2nd Marquess of Salisbury Edward Stanley, 15th Earl of Derby