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.
Princess Christine Louise of Oettingen-Oettingen Christine Louise of Oettingen-Oettingen (20 March 1671 in Oettingen – 3 September 1747 in Blankenberg) was Duchess of Brunswick-Lüneburg. She was the maternal grandmother of Holy Roman Empress Maria Theresa, Queen Elisabeth Christine of Prussia, Queen Juliane Marie of Denmark and Norway and Tsar Peter II of Russia; the maternal great-grandmother of Queen Marie Antoinette of France, Tsar Ivan VI of Russia and Francis, Duke of Saxe-Coburg-Saalfeld; the maternal great-great-grandmother of King Leopold I of Belgium and the maternal great-great-great-grandmother of Queen Victoria of the United Kingdom.