HM George I's 11-Great Grandfather. U.S. President [McKINLEY]'s 14-Great Grandfather. PM Churchill's 18-Great Grandfather. Lady Diana's 18-Great Grandfather. PM Cameron's 17-Great Grandfather. HRH Albert II's 20-Great Grandfather. Louis XVII's 15-Great Grandfather. Poss. Jamie's 19-Great Grandfather.