Kathleen Kennedy (1920 - 1948), Marchioness of Hartington, was the daughter of Joseph P. Kennedy, Sr and sister of U.S. president John F. Kennedy. She married William Cavendish (1917-1944), Marquess of Hartington and son of the 10th Duke of Devonshire, who was killed in action in World War II. She died in an airplane crash four years later.

See also: Kennedy family