(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