What American Socialite married the elder son of Edward Cavendish?
William Cavendish, Marquess of Hartington:  He was the elder son of Edward Cavendish, 10th Duke of Devonshire, and his wife, Lady Mary Gascoyne-Cecil. Kathleen Cavendish, Marchioness of Hartington: Kathleen Agnes Cavendish, Marchioness of Hartington ("née" Kennedy; February 20, 1920 – May 13, 1948), also known as "Kick" Kennedy, was an American socialite.
i don't know