Carlo Bounaparte (1746–1785). Had 13 children: 4 who became monarchs.
Joseph (1768–1844) King of Naples (1806–08) & King of Spain (1808–13)
Napoleon (1769–1821) Emperor of the French (1804–14 & 1815) & King of Italy (1805–14)
Louis (1778–1846) King of Holland (1806–1810)
Jerome (1784–1860) King of Westphalia (1807–13)
So there were four brother monarchs from 1807–1810. And some of their sisters became 'sort of' monarchs.
Élisa (1777–1820) was Princess of Piombino (1805-1814) and Grand Duchess of Tuscany (1809–1814)
Pauline (1780–1825) was sovereign Duchess of Guastalla for a few months in 1806.
Caroline (1782–1839) married Joachim Murat (1767–1815) who was grand duke of Berg (1806–1808) and King of Naples (1808–1815).
So that makes 4 to 7 Bonaparte monarchs. And from 1811-1814, and in 1815, Napoleon II had the title of King of Rome.
Emperor Louis I (778–840) had four sons who became Kings.
Lothair I (795–855), King of Middle Francia (840-855) and Emperor (817–855)
Pepin (797–838), King of Aquitaine (817–838)
Louis II the German (c.806–876), King of East Francia (843–876)
Charles the Bald (823–877), King of West Francia (840–877), Emperor (875–877)
Their sons included:
Louis II (825–875), King of Italy (844–877), Emperor (850–875)
Lothair II (835–869), King of Lotharingia (855–869)
Charles (845–863), King of Provence and Burgundy (855–863)
Pepin II (823–>864), King of Aquitaine (838–851/852)
Charles, brother of Pepin II (825/830–863), Archbishop of Mainz
Caroloman of Bavaria (c.830–880), King in Bavaria (876–879), King of Italy (877–879)
Louis III, the Saxon (830/835–882), King of Saxony (876–882), King in Bavaria (880–882)
Charles III (839–888), King in Swabia (876–887), in Italy (880–887), East Francia (882–887), West Francia (884–887), Emperor (881–887)
So eight first cousins became kings but not all at the same time. The reign of Louis II the German overlapped with the reigns of four of his nephews but no more than three at a time, and with his brother Charles the Bald while those nephews were kings, making up to five kings in the family.
The reigns of the three sons of Louis the German overlapped with their uncle Charles the Bald in 876–877.
For 8 years from 855 to 863 the reigns of three sons of Emperor Lothair I overlapped with the reigns of their two uncles Louis II the German and Charles the Bald, making five kings in the family.
Another, ninth, grandson of Louis I (on his mother's side) and first cousin, was Bergengar I (c. 845–924) who became King of Italy (with rivals from time to time) from 887–924 and Emperor 915–924. I note that Berengar I was killed 101 years after his first cousin Pepin II was born and 82 years after Pepin II became a king.
King Christian IX of Denmark (1818–1906) became known as "the father-in-law of Europe". His children included:
King Frederick VIII of Denmark (1843–1912)
Alexandria (1844–1925), married King Edward VII of England
King George I of Greece (1845–1913)
Dagmar (1847–1928), married Tsar Alexander III.
Thyra (1853–1933), married crown prince Ernst August of Hanover
His monarchial grandchildren included:
King Christian X of Denmark (1870–1847), r. 1912–1947
King Haakon VII of Norway (1872–1957), r. 1906–1957
King George V of the United kingdom (1865–1936), reigned 1910–1936
King Constantine I of Greece (1868–1923), r. 1913–1917 & 1920–1922
Tsar Nicholas II of Russia (1868–1918), r.1894–1917
(?) Grand Duke Michael (1878–1918) who technically might have been Tsar for a few hours
So the 5 first cousins & brothers reigned at the same time for 4 years from 1913–1917.
I may have other examples later.
Oct. 5 2022.
Fourth Contender: Queen Victoria and Prince Albert.
one) Princess Victoria, Empress (consort) of Germany 1889.
two) Edward VII,KIng of the Uk 1901-1910.
three) Princess Alice, Grand Duchess (consort) of Hesse 1877-1878.
four) Prince Albert, reigning Duke of Saxe-Coburg & Gotha 1893-1900.
five) Princess Helena - husband not a ruler.
Six) Princess LoOuise. Husband not a ruler.
Seven) Prince Arthur. Not a ruler.
eight) Prince Leopold. Not a ruler.
nine) Princess Beatrice. Husband not a ruler.
So four became rulers or consorts of rulers, but one at a time.
Wilhelm ii German Emperor 1889-1918.
Princess Charlotte Duchess (consort) of Saxe-Meiningen 1914-1918.
several who were not rulers.
Princess Sophia, Queen (consort) of the Hellenes 1913-1917.
Princess Margaret, Queen (consort)of Finland 1918.
George V King of the UK 1910-1936.
Several who were not rulers.
Princess Maud Queen (consort) of Norway 1905-1938.
several who were not rulers.
Ernst, Grand Duke of Hesse and by Rhine 1892-1918.
Alexandria, Empress (consot) of Russia 1894-1917.
Princess Marie, Queen (consort) of Rumania 1914-1927.
Princes Viktoria Melita Grand Duchess (consort) of Hesse & By Rhine 1894-1901.
several who were not not rulers.
Charles Duke of Saxe-coburg & Gotha 1900-1918.
Princess Victoria Eugenie Queen (consort) of Spain 1906-1931
So the grandchildren of Victoria included 2 who were monarchs of independent countries, 6 who were consorts of monarchs of independent countries, 2 who were rulers of dependent realms, and 2 who were consorts of rulers of dependent realms. From 1914-1917 11 were rulers of independent or dependent countries or their spouses. but there were only 2 rulers of independent countries at a time, Wilhelm II and George V 1910-1918.
Fifth contender. Sancho III The Great (992/96-1035), king of Pamplona/Navarre from 1004 to 1035. He greatly expanded his realm and divided his lands among his sons.
- Garcia Sanchez III, King of Pamplona 1035-1054.
- Fernando Sanchez, Count of Castile 1035-1065, kIng of Leon 1037-1065.
- Gonzalo Sanchez, king of Sobrarbe and Ribagorza 1035-1043.
- Ramiro I Sanchez, King of Aragon 1035-1063.
His grandchildren Included:
- Sancho IV Garces, King of Pamplona 1054-1076.
- Sancho II, King of Castile 1065-72, Galicia 1071-72, Leon 1072.
- Alfonso VI, King of Leon 1065-1072, 1072-1109, King of Galicia and Portugal, King of Castile 1072-11009, Emperor of all Hispania 1077-1109.
- Garcia King of Galicia 1065-1072.
- SAncho V Ramirez King of Aragon 1063-1094, king of Pamplona 1076-1094.
Thus from 1065 to 1072, there were five brothers and first cousins who were kings at the same time.
Sixth Contender: Yaroslav the Wise, Great Prince of Kievan Rus (r/ 1019-1054).There were a number of princepalities in kievan Rus, with a great prince as the overlord.
- Vladimir, Prince of Novgorod 1036-1052.
- Iziaslav I, Prince of Turov 1045-52, Great Prince 1054-1076.
- Sviatoslav II, Prince of Volhynia 1040-1054, Prince of Chernigov 1054-76, Great Prince 1073-76
- Vsevolad I, Prince of Pereyaslav 1054-73, Prince of Chernigov 1073-78, Great Prince 1078-1093.
- Igor, Prince of Volyn 1054-1057 Prince of Smolensk 1057-1090.
- Vyacheslav, Prince of Smolensk 1054-1057.
Three of Yaroslav's daughters married foreign rulers.
Elisev (1025-c.1067) married Harald III Hardrada, king of Norway from
Anastasia (c.1023-1074/94) married King Andrew I of Hungary (ruled 1046-1060).
Anne (c. 1030-1075) married King Henry I of France (r. 1031-1060).
So from 1046-1060, three of Yaroslav's daughters were queens (consort), wives of reignng kings. And from 1045 to 1052 three of Yaroslavs's sons were princes, and from 1054 to 1076 four of Yaroslav's sons were princes.
So if Rus princes count as monarchs, and if queens consort count, from 1046 to 4052 six of Yaroslav's children were monarchs at thes ame time, and from 1054 to 1060 seven of Yaroslav's children were monarchs at the same time.
Added January 15-16 2023 Grandchildren of Yaroslav the Wise.
Rostislav Vladimirovich Prince of Volhynia and Hallich 1057-64, Prince of Tmutarikan 1064-1066.
Adelheid of Hungary (c.1040-1062) married Wratislav II (c. 1035-1092) Duke of Bohemia (1061-1085) and King of Bohemia (1085-1092).
Salomon (1051-1087) King of Hungary 1063--1074).
Mstislaw Isjaslawitsch Prince of Plock (d. c. 1069).
Jaropolk (c.1050-1087) Prince of Turov and Volyn 1078-1087, "King of Rus".
Sviatopolk II (c.1050-1113), Prince of Novgorod 1078-88, Prince of Turov 1088-93, Great Prince 1093-1113.
Jarsolav Prince of Tschernigov, Rjasan, & Murom.
Vladimir II Monomakh (1053-1125) prince of various principalities 1073-1113, Great Prince of Kiev 1113-1125.
Eupraxia of Kiev (c.1067-1109) married secondly 1089 Henry IV (1050-1106) King of the Romans 1055-1084, Emperor of the Romans 1084-1105.
Ingigerd of Norway.
Married c. 1067 Olaf I "Hunger" king of Denmark 1086-1095,
& second c.1095/96 Philip, king of Sweden c.1105/10-1118.
Philip I (<102-1108) King of France 1067-1108.
David Igorjewitsch (c. 1058-1112) Prince of Volyn (1086-1099).
So from 1154 to 1157 while Vyacheslav was Prince of Smolensk, 5sons of Jaroslav the Wise ruled principalties and three daughters were married to kings. However, only Grand Prince Iziaslav I and the three kings were sovereign monarchs.
And from 1063 to 1066 four sons and one grandson of Jaroslav the Wise ruled principalities, while one daugther was married to a king, and two grandsons were kings. But only Grand Prince Iziaslav I and the three kings were sovereign monarchs.
To be continued