HRH Charles's 18-Great Uncle. Louis XVII's 14-Great Uncle. HM Juan Carlos' 23-Great Grandfather. Philippe of Belgium's 23-Great Grandfather. HM Beatrix's 17-Great Grandfather. HM Constantine II's 18-Great Grandfather. Wm. von Bismarck's 14-Great Grandfather. `Red Baron' Richthofen's 16-Great Grandfather.