If you’ve ever found yourself confused by the genealogy of European royal families—who married whom, which king was related to which queen, how everyone seems distantly connected—you’re not alone. The royal families of Europe are so tangled up in marriage, inheritance, and alliance that you’d need a genealogist and a flow chart to fully understand it all. The funny part? This wasn’t accidental. European royalty deliberately married into each other’s families for centuries, using marriage as a tool of statecraft. The result is a continent where nearly every monarch is someone else’s cousin, and where a single family’s ambitions could reshape the entire continent.

The Habsburgs: The Family That Couldn’t Say No to Marriage

If there’s one family that truly embodies the “marry your way to power” strategy, it’s the Habsburgs. This Austrian dynasty didn’t conquer Europe so much as marry it. Their motto, allegedly, was “Others wage war; you, happy Austria, marry,” and they took it seriously. For centuries, the Habsburgs used strategic marriages to expand their power across Spain, Italy, the Netherlands, Hungary, and more.

The Spanish Habsburgs are a perfect example of how this strategy could go magnificently wrong. When King Charles II of Spain inherited the throne in 1665, he was the product of so much Habsburg inbreeding that he had the famous “Habsburg jaw”—a severe underbite caused by generations of cousins marrying cousins. Charles II was so inbred that he was infertile, which triggered a succession crisis and led to the War of Spanish Succession (1701-1714), an enormous European conflict fought basically over which other family got to claim Spain.

The Habsburgs married their way into Spain, into the Holy Roman Empire, into Hungary and Bohemia. For centuries, they were the most powerful dynasty in Europe, not because they were particularly militarily brilliant, but because they understood that marriage treaties could accomplish what armies took decades to achieve. An Austrian archduchess married to a French king was a living peace treaty.

The Bourbons: Competing with the Habsburgs

The Bourbon family is equally obsessed with strategic marriage, though they came to prominence later. The Bourbons ruled France, Spain, and Naples, and through various marriages, had tentacles extending into other kingdoms. When the Habsburg Charles II died without direct heirs, a Bourbon prince inherited Spain, which caused such panic among other European powers that they fought the War of Spanish Succession to prevent French Bourbon and Spanish Bourbon from becoming a combined superpower.

Even today, the Kings of Spain are Bourbons, making them relatives of the French royal family (which was overthrown in 1789 but whose descendants still exist). The Spanish monarchy is very much aware of its Bourbon heritage, and the current king, Felipe VI, is a direct descendant of this ancient dynasty.

Queen Victoria: The Grandmother of Europe

If the Habsburgs and Bourbons were the older generations of European royal inbreeding, Queen Victoria was the grand architect of 19th-century royal connections. Victoria reigned Britain from 1837 to 1901, and she had nine children. She married each of them—or married them off—into other European royal families, earning her the title “Grandmother of Europe.”

Her daughters and sons married into the royal families of Germany, Russia, Greece, and Scandinavia. Her grandsons included Kaiser Wilhelm II of Germany and Tsar Nicholas II of Russia. Her grandchildren were scattered across the European thrones. This is actually remarkable to contemplate: some of the worst enemies in World War I—Britain, Germany, and Russia—were all ruled by cousins who shared the same grandmother. Tsar Nicholas II and King George V of Britain were first cousins (their mothers were sisters), and Kaiser Wilhelm II was their cousin as well.

In a haunting twist of history, Victoria’s great-grandchildren would fight each other across trenches during World War I. Queen Victoria’s 19th-century family tree became World War I’s family feud.

The Scandinavian Royals: A Tangled Northern Web

The three Scandinavian countries—Denmark, Sweden, and Norway—have royals so interrelated that you almost need a program to keep track. The current King of Denmark is descended from Christian IX, who was so prolific in spreading his children to other thrones that he’s sometimes called “the Father-in-Law of Europe.”

Denmark’s Christian IX married off his children to rule Greece, Russia, and Britain. His daughter Alexandra married the future King Edward VII of Britain, making the Danish and British royal families cousins. His son George I became King of Greece. The Norwegian and Swedish royals are equally tangled with Danish and with each other—at one point, Sweden and Norway shared a monarch through a personal union.

Today, the Scandinavian royals remain close, and you’ll see them at each other’s coronations and weddings. The current King of Sweden, Carl XVI Gustaf, is related to both the Danish and Norwegian monarchs. Meanwhile, Princess Mary of Denmark is Australian-born and married into the Danish royal family—showing that even in the modern era, royal marriage is an important tool of international relations.

Who Still Has a Monarchy and Who Doesn’t?

Of our twelve countries, six still have working monarchies: Denmark, the Netherlands, Spain, Sweden, Norway, and Greece. The others—France, Germany, Italy, Portugal, Poland, and the Czech Republic—became republics (or returned to being republics after communist rule).

The French revolution in 1789 abolished the French monarchy, though royalist pretenders existed for decades afterward. Germany’s monarchy fell during the chaos of World War I; Kaiser Wilhelm II abdicated in 1918 and fled to the Netherlands. Italy briefly had a monarchy (abolished in 1946 after World War II), and Portuguese royalty fell during the 1910 revolution.

Poland and the Czech Republic are interesting: they had medieval monarchies, but those were abolished during Soviet rule and never restored. After communism fell in 1989, these countries chose to remain republics rather than resurrect their old royal families.

The monarchies that survived tend to have adapted well to democracy. The Dutch, Scandinavians, Spanish, and Greeks have constitutional monarchies where the royals reign but don’t rule—they’re the ceremonial head of state while a prime minister handles actual governance. It’s a formula that seems to work well for modern Europe.

Royal Marriages as Peace Treaties

Throughout European history, royal marriages were used as peace tools. When France and England were at each other’s throats, they’d negotiate a royal marriage to cement an alliance. When two rival kingdoms needed to end a conflict, a marriage between their heirs was often the solution.

The most famous might be the marriage between Isabella of Castile and Ferdinand of Aragon in 1469. Their union eventually led to the unified kingdom of Spain—the first truly unified Spanish state. This was a marriage that literally created a nation.

Similarly, the marriage of Mary Queen of Scots to the French Dauphin was meant to unite Scotland and France against England. Royal women in particular were often used as diplomatic tools, sent to marry foreign princes to cement alliances. Eleanor of Aquitaine married first the King of France and then the King of England, giving her territory and influence across Western Europe. Her sons went on to fight each other in conflicts that shaped European history.

The Windsor Name Change: Hiding German Roots

Here’s a fun historical footnote: the British royal family changed its name. The current British royal family is the House of Windsor, but that name is only about 100 years old. Before 1917, they were the House of Saxe-Coburg and Gotha—a thoroughly German name that made sense because Queen Victoria’s husband, Prince Albert, was German.

But during World War I, when Britain was fighting Germany, having a royal family with a German name seemed rather awkward. So in 1917, King George V simply changed the family name to Windsor (after Windsor Castle). It’s one of history’s most straightforward examples of royal rebranding, and it worked—the Windsor name stuck, and today’s British royals are Windsors.

The Modern Royal Network

Today’s European royals are remarkably intertwined. The King of Spain is related to the French royal pretenders (who don’t rule). The Norwegian, Danish, and Swedish royals are all cousins. The British royal family remains connected to royals across Europe. Recent royal weddings have shown these connections: when Prince William married Catherine Middleton in 2011, royals from across Europe attended. When the King of Spain’s daughter got married, you saw royals from Greece, the Netherlands, and elsewhere in attendance.

Royal marriages continue to happen, though they’re far less politically important than they once were. When Prince Philippe married Letizia Ortiz (a Spanish TV journalist), it showed that royal marriages aren’t just tools of statecraft anymore—modern royals can marry for love, even across social boundaries.

The Lesson: Power Through Connection

Understanding European royal families teaches you something fundamental about how the continent developed. For centuries, Europe was ruled by family networks. Wars were family feuds. Peace treaties were family compromises. A marriage between a French princess and a Spanish prince could reshape the balance of power.

Queen Victoria, the Habsburgs, the Bourbons, the Scandinavian dynasties—they all understood that marriage was power. The reason so many European countries have cousins ruling them isn’t accident; it’s the result of centuries of deliberate intermarriage. And while modern Europe has moved beyond absolute monarchies and royal rule, these family connections remain, reminding us that European history is, in many ways, a family story written in blood, treaties, and crown jewels.

Next time you’re traveling in Europe and see a statue of a 19th-century monarch, glance at the plaque. Chances are good that monarch is distantly related to one of the current reigning royals you might encounter in another country a few hours’ drive away.