John Albert William Spencer-Churchill, 10th Duke of Marlborough (Nov 1934); shortly after assuming the title. He was the son of Consuelo Vanderbilt and "Sunny" Charles Richard John Spencer-Churchill, 9th Duke of Marlborough.
Consuelo Vanderbilt | The Duchess of Marlborough (c. 1899) with her two infant sons: (l) Lord Ivor Charles Spencer-Churchill, b. 14 Oct 1898; (r) John Albert William Spencer-Churchill, Marquess of Blandford, b. 18 Sep 1897 (later the 10th Duke of Marlborough).