HRH Charles's 12-Great Grandfather. PM Cameron's 14-Great Grandfather. HM Juan Carlos' 12-Great Grandfather. Philippe of Belgium's 13-Great Grandfather. HM Manuel II's 12-Great Grandfather. Grand Duke Henri's 13-Great Grandfather. HM Margrethe II's 12-Great Grandfather. HM Beatrix's 12-Great Grandfather. HM Constantine II's 12-Great Grandfather. HM Carl XVI Gustaf's 12-Great Grandfather. HM Harald V's 12-Great Grandfather. Ksr Wilhelm II's 10-Great Grandfather. Boris Johnson's 14-Great Grandfather.