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.
Francis II, Holy Roman Emperor Francis II (German: "Franz" ; 12 February 1768 – 2 March 1835) was the last Holy Roman Emperor, ruling from 1792 until 6 August 1806, when he dissolved the Holy Roman Empire of the German Nation after the decisive defeat at the hands of the First French Empire led by Napoleon at the Battle of Austerlitz. In 1804, he had founded the Austrian Empire and became Francis I, the first Emperor of Austria, ruling from 1804 to 1835, so later he was named the one and only "Doppelkaiser" (double emperor) in history.