Royal Intermarriage In Medieval and Modern Europe

Royal Intermarriage In Medieval and Modern Europe
Louis XIV of France and Philip IV of Spain meeting at the Isle of Pheasants for the signing of the Treaty of the Pyrenees, which, in part, arranged the marriage of Louis with Philip's daughter Maria Theresa.

Centuries of royal intermarriage have shaped medieval and early modern Europe. 

Contrary to the modern perception of marriage as a bond of love between a couple and  being primarily centered around romantic bases, it was seen much differently back in the medieval ages and even in the early modern era. As marriage for political, economic, societal and diplomatic reasons is a pattern that is seen among European monarchs for centuries.

What is “Royal Intermarriage” ?

Royal intermarriage is the practice of members of a ruling royal house marrying into other foreign royal families.

It was often done as a part of a strategic diplomacy in order to promote national interests and has been a matter of political policy. It eventually became a tradition in monarchies. Although this practice is believed to date back to the Late Bronze Age and was not common in other parts of the world, it was especially prevalent in medieval Europe as monarchs wanted international expansion of their influence on behalf of themselves and their dynasties. Royal marriages were fundamentally about dynastic unions, reinforcing political allegiances and establishing new political alliances. This practice contributed to the notion that it was socially, as well as politically, disadvantageous for members of ruling families to intermarry with their subjects and pass over the opportunity for marriage into a foreign dynasty.

Kinship by marriage is also to enhance territorial gains by reinforcing a legal claim to a foreign throne from the side of an heiress, especially when the monarchs fail to produce male offspring.

The Habsburgs: Expansion via Inheritance

Perhaps the greatest dynasty of  Europe, the Habsburgs essentially used arranged marriages to gain political privileges in certain areas and monarchies in Europe. A dynasty marked by more victories achieved through cunning political sensitivity rather than by military glory, the Habsburgs always settled their power in their family.

In ⅩⅤth century, the Hungarian King wrote in a letter

“Let the others make war. You, happy Austrians, get married. What Mars gives to others, Venus delivers to you !”

This became the motto of the marriage alliance policy of the Habsburgs as nations and kingdoms joined their family possessions; Spain and Portugal with their overseas territories, Hungary, Croatia, Bohemia, Milan, Tuscany, Areas of northern Italy, the Netherlands, Naples, Sicily… The royal House’s dream was a universal monarchy which seemed imminent at the time.

The battlefields were not mainly responsible for the power the Habsburgs achieved but rather the foreign marriages.

The first master of this marriage art was Maximilian I, Holy roman emperor, his arranged marriage to the only daughter of the Duke of Burgundy by his father and his second marriage bequeathed him dominions, let the family conquer new lands but antagonized the French.

Philip I and Joanna of Castile

Maximilian continued the marriage policy through his children and grandchildren to further antagonize France. Initially, he arranged a double wedding  between his son Philip the fair and Joanna the mad, queen of Castile and later queen of Aragon.

By a stroke of luck, the son of the two couple Charles V of the Holy Roman Empire or Charles I of Spain became the first monarch “over whose empire the sun never set”. He inherited notably Spain and its colonial empire, the seventeen provinces of the Netherlands, the kingdom of Naples and Austrian possessions; elected emperor of the Romans in 1519, he was the most powerful monarch of the first half of the 16th century.

Charles V of the Holy Roman Empire

His Heir, Philip II became king of Portugal after the extinction of the “Aviz House” apart from all the lands inherited through his father.

Following the Death of the king of  Hungary and Bohemia, Ferdinand, another son of Philip and Joanna, married to the king’s sister and brother of the queen, claimed the crown of Bohemia and Hungary which became land of the Habsburg crown and claimed by all the Habsburg rulers that followed until the last Austrian emperor.

Ferdinand I

Ferdinand later became Holy Roman Emperor, ruler of Austria and its adjacencies, King of Bohemia, Hungary and Croatia.

Moreover, women also played an important role in expanding the Family’s influence like Mary, Queen of Hungary and Eleanor of Austria, Queen of France. The archduchesses were valuable bargaining chips in the marriage negotiations and treaties as well as nominal rulers whether wedded or not as they maintained the possessions their uncles, brothers or fathers could not manage. As governing is a family matter when it comes to the Habsburgs.

With this, the Habsburgs ruled Europe and the world through two lineages of the same family ; one that incorporated the lords of Spain and its colonial possessions and the other incorporating Holy Roman Emperors and rulers of Central Europe.


Later on, a lack of same-level suitors was visible because of the hostility towards the French as well as protestants. This certainly concerned the Spanish lineage which had more inter family marriages. This drove to family exhaustion until a few decades later, the Spanish Habsburg line became extinct after the Death of Charles II without leaving any heirs. The Spanish crown and its colonial dominions were lost forever and the House of Bourbon took over it.

“Habsburg Jaw”

Despite being widely successful, the marriage policy left serious impact on the family genetics of the Habsburgs such as the famous “Habsburg Jaw”. Like other fellow nobles, they sought to marry relatives to preserve the royal blood and create new political alliances. Inbreeding with the lack of new blood accentuated undesirable physical characteristics, diseases and more infant mortality in the family.

Other European Examples

When royal intermarriage is done between two monarchs, in most cases, there is a special agreement and negotiations to be done. These treaties include the inheritance rights on the maternal, paternal and the children’s side.

Mary and Francis II
  • The Franco-Scottish treaty (1558) that led to the marriage of Mary, Queen of Scots and Francis II, heir to the French throne stated that if the future queen consort were to die, the Scottish throne would fall under the French crown and if the Kingdom of Scotland was ever attacked by England, France would come to its aid and vice-versa.
Mary, Queen of England
  • The marriage between Philip II, king of Spain, and Mary, Queen of England, included an agreement that states that the paternal possessions (territories) would pass down to the King’s son from his first marriage and  the maternal possessions would pass down to the couple’s future children.

Queen Victoria: the Grandmother of Europe 

Queen Victoria and consort Albert (who were first cousins themselves) wanted to maintain Great Britain’s political power in Europe and reinforce it by marrying their children to monarchs across Europe as well as ties with important states. The Eldest daughter was married to the heir of the Prussian throne. Being the strongest of the German states, Victoria and Albert expected it to be the one leading the German unification and building great ties with the newly unified Germany.

Five of their children also married into German royalty while the heir Edward VII married a Danish princess, sister of the king of Greece which was also two important European states. One of their sons also married the daughter of the Russian Tsar.

Queen Victoria and her Family

7 of their 42 grandchildren were on royal thrones; UK, Germany, Russia, Spain, Norway, Greece, and Romania, and most European royalty shared Queen Victoria’s blood thanks to their use of marriage to establish political influence, which got her the nickname “Grandmother of Europe”.

Post-WW1 Era 

WW1 essentially ended the era of Monarchy in Europe. Today, Royal intermarriage is very rare, and royal dynasties pretty much avoid marrying people from other royal houses because the majority of European royalty share the same blood and ancestors. This is to avoid inbreeding as a result of the widely common genetic pool.

Most of them opt for people from titled noble families or marrying commoners, which became more common and often the case.

Among current rulers, only the United Kingdom and Liechtenstein have monarchs from foreign royalty.


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