For several centuries - especially from the 16th to the early 20th century - Europe’s royal families were deeply interwoven....
HISTORY
For several centuries - especially from the 16th to the early 20th century - Europe’s royal families were deeply interwoven. Marriages between cousins and other close relatives were not only accepted but actively pursued. These dynastic unions were rarely about romance or personal preference; they were strategic decisions aimed at preserving power, forging political alliances, maintaining peace, legitimising territorial claims and ensuring succession within a narrow elite.
Because royalty was expected to marry within their own rank, the pool of eligible spouses was limited. Consequently, intermarriage among close kin became routine. Queen Victoria and her husband Prince Albert, for example, were first cousins. Their children and grandchildren married into nearly every royal house on the continent, earning Victoria the title ‘the grandmother of Europe’.
By the early 20th century, three of Europe’s most powerful rulers - Britain’s King George V, Germany’s Kaiser Wilhelm II, and Russia’s Tsar Nicholas II - were all first cousins, directly descended from either Victoria or her uncle, King Leopold I of Belgium.
The Habsburgs and the cost of inbreeding
Perhaps no dynasty exemplifies this pattern better than the Habsburgs, who ruled over Austria, Spain and parts of Central Europe. The Habsburgs deliberately married within their own bloodline to consolidate power and preserve territory. This led to severe genetic consequences. One notable result was the ‘Habsburg jaw’ - a prominent underbite caused by generations of inbreeding. The most tragic example was Charles II of Spain. Beset by numerous physical and mental health issues, Charles died without an heir in 1700. His death ignited the War of the Spanish Succession, a major conflict involving most of Europe’s great powers.
Haemophilia and the Romanovs
In Russia, the Romanov dynasty faced a different genetic burden: haemophilia. This inherited blood disorder, which prevents clotting, entered the family through Queen Victoria’s lineage.
Her daughter Alice passed it to her granddaughter Alexandra, who married Tsar Nicholas II. Their son, Tsarevich Alexei, suffered from the condition. His illness profoundly influenced the royal family’s private life and public image. Alexandra turned increasingly to the mystic Rasputin, believing he could alleviate her son’s suffering. Rasputin’s controversial role at court fuelled public suspicion and undermined confidence in the monarchy during a period of growing unrest - ultimately contributing to the Romanovs’ downfall in the Russian Revolution.
The Church’s role in royal unions
Religion also played a central role in the pattern of cousin marriage among royals. In medieval and early modern Europe, marriage was more than a legal or social contract - it was a sacred sacrament overseen by the Church. The Catholic Church had strict rules on consanguinity, forbidding unions between people within seven degrees of kinship. Under the Church’s system of calculating relatedness, this could include even distant relatives such as fourth or fifth cousins. These laws aimed to prevent hereditary illness, reduce the concentration of power within extended clans and encourage alliances beyond narrow family circles.
By the 12th century, these rules were slightly relaxed. The prohibited degree of kinship was reduced to the fourth degree - meaning first cousins could marry, but only with a papal dispensation. Such dispensations became a necessity for Europe’s royals. Given the limited pool of noble partners, monarchs frequently found themselves wishing to marry someone technically too closely related. Instead of abandoning the match, they would petition the Pope for an exemption.
A papal dispensation served several purposes. It legitimised the marriage in the eyes of both the Church and the public. It ensured that the children born of the union would be considered lawful heirs. And it bolstered the monarch’s image as a Christian ruler obedient to ecclesiastical authority. For example, Philip II of Spain married his niece, Anna of Austria, with full papal approval - part of a broader Habsburg effort to keep power firmly within the family. This marriage, however, deepened the dynasty’s genetic problems.
Another well-known case is that of England’s Henry VIII. His marriage to Catherine of Aragon, the widow of his brother Arthur, required a special dispensation due to its biblical prohibition.
Years later, Henry used doubts about the validity of that dispensation to justify his request for an annulment - one that the Pope refused to grant. The ensuing dispute led Henry to sever ties with Rome and establish the Church of England, forever altering the religious landscape of Britain.
The Church itself walked a delicate line. It had theological principles to uphold, but it also relied on the patronage and protection of powerful monarchs. As a result, the granting of dispensations was often influenced by political realities. While the Church maintained its rules, it made exceptions when the stakes were high, revealing the complex interplay between spiritual authority and temporal power.
A shift in values
By the early 20th century, the practice of cousin marriage among royals began to wane. Several factors contributed to this shift. Scientific advances in genetics and medicine exposed the health risks associated with inbreeding. Conditions such as haemophilia, infertility and physical deformities were no longer viewed as divine misfortunes but as preventable outcomes of consanguinity.
Political change also played a significant role. The decline of absolute monarchies and the rise of constitutional systems diminished the need for dynastic alliances. Monarchs transitioned from ruling figures to symbolic ones, and royal marriages became less about statecraft and more about personal choice.
The First World War delivered a further blow to royal interconnectivity. Monarchies collapsed in its aftermath in Germany, Austria and Russia, erasing entire royal lines. Nationalist sentiment surged, and loyalty to one’s country replaced loyalty to royal blood. Marriages to foreign royals began to seem suspect rather than desirable.
Modern royals
Cultural values evolved alongside these political changes. Modern monarchs often choose spouses from outside noble or royal circles, reflecting broader social ideals. Spain’s King Felipe VI married Letizia Ortiz, a former journalist. Norway’s Crown Prince Haakon wed Mette-Marit Tjessem Høiby, a commoner and single mother. In the British royal family, Prince William married Catherine Middleton, the daughter of self-made entrepreneurs, while Prince Harry married Meghan Markle, an American actress and a divorcée. These unions reflect a growing emphasis on personal compatibility, love and public relatability, rather than traditional aristocratic expectations.
Once the backbone of European diplomacy and empire-building, royal intermarriage has all but vanished. Yet its legacy remains visible - in the shared ancestry of today’s royal families, in the historical crises it sometimes triggered and in the enduring fascination it holds for historians and the public alike. The cousin-kings and queenly matchmakers of Europe’s past remind us that marriage, even at its most personal, was once a tool of statecraft.
