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.
Duc de Dalberg The title of Duc de Dalberg was created by the French Emperor Napoleon I on 14 April 1810 for Emmerich von Dalberg, the nephew of Karl Theodor von Dalberg, Prince-Primate of the Confederation of the Rhine and Grand Duke of Frankfurt. He died on 27 April 1833. His daughter and heiress married firstly Sir Richard Acton, 7th Baronet (by whom she was the mother of John Dalberg-Acton, 1st Baron Acton) and secondly Granville George Leveson-Gower, 2nd Earl Granville, but as the Duke had no sons, the title became extinct.