Poss. Lady Diana's 18-Great Uncle. HM Juan Carlos' 18-Great Grandfather. Philippe of Belgium's 18-Great Grandfather. Grand Duke Henri's 18-Great Grandfather. HM Margrethe II's 18-Great Grandfather. HM Beatrix's 14-Great Grandfather. HM Constantine II's 14-Great Grandfather. HM Carl XVI Gustaf's 14-Great Grandfather. `Red Baron' Richthofen's 12-Great Grandfather.