My brother mentioned a photo he saw of the monarchs from various countries in Europe, where the resemblance was readily apparent between them.

This got him to wondering and hence me to asking: When was the peak relatedness of monarchs in Europe? For simplicity, let's say "related" means first cousins or closer.

At what time were the most reigning monarchs related to each other to that degree?

(If this question is (A) much too difficult to answer without clearer definition, or (B) much too easy to answer given such and such a website, please let me know!)

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    My tip: Queeny Vicky and her offspring culminating in the gang of UK-George, Germ-Willy and raised to tsardom Nicky. Look at those faces… Sep 14 at 20:55
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    This is going to be kind of tough. For example, the legal stipulation since the Glorious Revolution that the UK monarch has to be Protestant (and the dynastic imperative that until quite recently mates have to be nobility, preferably royalty) drastically limited the available gene pool for the UK for the last 400 years, but it also served to somewhat isolate them from half the Royalty of Europe. So if you pick carefully chosen examples (eg: LLC's) you can discover that everyone you picked were first or second cousins. But these same folks were more distant from monarchs of Catholic nations.
    – T.E.D.
    Sep 14 at 21:09
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    What about 1809-1813: Napoleon as Emperor of France; Joseph as King of Spain; Jerome as King of Westphalia; Eugene (adopted, step-son) as King of Northern Italy; and Murat (step-brother) King of Naples. Sep 14 at 23:57
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    The Hapsburg family was famous for a high degree of inbreeding, leading to persistent physical peculiarities such as the "Hapsburg lip" in later generations. The family "tree" of Charles II of Spain is a frequently used for illustration, see the "Ancestry" section of the Wikipedia article, for example.
    – njuffa
    Sep 14 at 23:58
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    World War I has been referred to as "the deadliest family feud ever" for a reason.
    – Mark
    Sep 15 at 2:31

2 Answers 2


First contender:

  • Carlo Bounaparte (1746–1785). Had 13 children: 4 who became monarchs.

    1. Joseph (1768–1844) King of Naples (1806–08) & King of Spain (1808–13)

    2. Napoleon (1769–1821) Emperor of the French (1804–14 & 1815) & King of Italy (1805–14)

    3. Louis (1778–1846) King of Holland (1806–1810)

    4. 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.

    1. Élisa (1777–1820) was Princess of Piombino (1805-1814) and Grand Duchess of Tuscany (1809–1814)

    2. Pauline (1780–1825) was sovereign Duchess of Guastalla for a few months in 1806.

    3. 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.

Second Contender:

  • Emperor Louis I (778–840) had four sons who became Kings.

    1. Lothair I (795–855), King of Middle Francia (840-855) and Emperor (817–855)

    2. Pepin (797–838), King of Aquitaine (817–838)

    3. Louis II the German (c.806–876), King of East Francia (843–876)

    4. Charles the Bald (823–877), King of West Francia (840–877), Emperor (875–877)

    Their sons included:

    1. Louis II (825–875), King of Italy (844–877), Emperor (850–875)

    2. Lothair II (835–869), King of Lotharingia (855–869)

    3. Charles (845–863), King of Provence and Burgundy (855–863)

    4. Pepin II (823–>864), King of Aquitaine (838–851/852)

    5. Charles, brother of Pepin II (825/830–863), Archbishop of Mainz

    6. Caroloman of Bavaria (c.830–880), King in Bavaria (876–879), King of Italy (877–879)

    7. Louis III, the Saxon (830/835–882), King of Saxony (876–882), King in Bavaria (880–882)

    8. 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 seven 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 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 died 101 years after his first cousin Pepin II was born and 82 years after Pepin II became a king.

Third contender:

  • King Christian IX of Denmark (1818–1906) became known as "the father-in-law of Europe". His children included:

    1. King Frederick VIII of Denmark (1843–1912)

    2. Alexandria (1844–1925), married King Edward VII of England

    3. King George I of Greece (1845–1913)

    4. Dagmar (1847–1928), married Tsar Alexander III.

    5. Thyra (1853–1933), married crown prince Ernst August of Hanover

    His monarchial grandchildren included:

    1. King Christian X of Denmark (1870–1847), r. 1912–1947

    2. King Haakon VII of Norway (1872–1957), r. 1906–1957

    3. King George V of the United kingdom (1865–1936), reigned 1910–1936

    4. King Constantine I of Greece (1868–1923), r. 1913–1917 & 1920–1922

    5. Tsar Nicholas II of Russia (1868–1918), r.1894–1917

    6. (?) 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.

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    At the same time that Christian IX was becoming "the father-in-law of Europe", Queen Victoria was becoming the grandmother of Europe, with four grandchildren on various thrones plus five queen consorts.
    – Mark
    Sep 16 at 3:17

I think the Bourbons should be mentionned. In 1752, the French king was a bourbon (Louis the XV), the Spanish king was a bourbon (Fernando VI - sort of cousin to Louis the XV), the king of Sicily was a bourbon (Charles V - sort of cousin to Louis the XV and brother of Fernando), the duke of Parma was a bourbon (Filippo di Borbone - cousin to Louis the XV), the Prince of Piemont-Savoie was the son of a Bourbon mother (Charles-Emmanuel III) and there just was a Bourbon married to the heiress of the Portuguese crown (Gabriel de Borbón y Sajonia).

You can find all of them here by searching a bit (wikipedia link to a simplified genealogy tree) some of them switched titles after marriage or death of their relatives, so only their most prestigious title is listed. But you can find them all, with a bit of time. And that's only the easy titles that I found, I didn't search all of the married girls of the house, since this is harder. But there more and more cousins if you dig that way. This was basically their "prime", even though they managed to get the Brazilian empire at one point, some germanic houses managed to wrestle more and more titles in Europe and their influence wanned a bit.

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