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.
Prince Christian of Schleswig-Holstein Prince Christian of Schleswig-Holstein (Frederick Christian Charles Augustus; 22 January 1831 – 28 October 1917) was a minor Danish-born German prince who became a member of the British Royal Family through his marriage to Princess Helena of the United Kingdom (25 May 1846 – 9 June 1923), the fifth child and third daughter of Queen Victoria and Prince Albert of Saxe-Coburg-Gotha.