Kathleen Kennedy (1920 - 1948, third from left) with her husband William Cavendish, Marquess of Hartington (1917 - 1944), after their wedding in London, 6th May 1944. Kathleen Kennedy was the daughter of former US Ambassador to Britain, Joseph Kennedy, and younger sister of future U.S. President John F. Kennedy. After her marriage she became Kathleen Cavendish, Marchioness of Hartington. (Photo by Keystone/Hulton Archive/Getty Images)