Arthur Gerald Wellesley, Earl of Mornington, is the great-great-grandson of what  last German Emperor ("Kaiser") and King of Prussia?
Arthur Wellesley, Earl of Mornington Arthur Gerald Wellesley, Earl of Mornington (born 31 January 1978 at St Mary's Hospital in Paddington, London) is the son of Charles Wellesley, 9th Duke of Wellington. The Wellesleys are an aristocratic Anglo-Irish family. Through his mother, Antonia von Preussen, Duchess of Wellington, he is great-great-grandson of Kaiser Wilhelm II. As a descendant of Queen Victoria, he is eligible to succeed to the British throne.
Duke of Marlborough (title) Duke of Marlborough ( ) is a title in the Peerage of England. It was created by Queen Anne in 1702 for John Churchill, 1st Earl of Marlborough (1650–1722), the noted military leader. In historical text, it is often to him that an unqualified use of the title refers. The name of the dukedom refers to Marlborough in Wiltshire. It is one of the few titles in the peerage which allows for "suo jure" female inheritance, and the only current dukedom to do so.