The relationships between European royal families today are so intertwined that it is hardly possible to distinguish between them. All of them are related to each other to some degree, a result of centuries of royal marriages designed to increase families’ power, influence, and wealth.
Best known for this practice are perhaps the most notable European royal family, the Habsburgs. Their marriage strategy is best described by saying “Bella gerant alii, tu felix Austria, nube! – “Let others wage war. You, lucky Austria, shall marry!” And so they did. At one point, through thrones of Austria and Spain, the Habsburgs ruled over the majority of today’s Europe. Fortunately for the rest of the countries and with families, even royal ones, being what they are, they rarely saw eye to eye and often fought each other. Today, the head of the house is Karl von Habsburg.
Intermarrying among relatives wasn’t just Habsburg thing. Many noble families practiced it. This has resulted in many interesting cases throughout history. For instance, a normal person has 1024 ancestors over 11 generations. King Alfonso XIII of Spain only had 111. Henri, Count of Paris’ all 4 grandparents were grandchildren of Louis Philippe I. Inbreeding has left some serious consequences, but royals, just like any other family, don’t like to talk about it. But as the time change, so do the noble families. There are plenty of examples of commoners gaining entry into a royal line by marriage. Edward VIII even abdicated his throne on account of a commoner, American Wallis Simpson. Grace Kelly’s marriage to Prince Rainier of Monaco is a more recent example.
Of all the countries that have King or a Queen, 10 are European ones, 12 if you count Andorra and Vatican. Out of those 10, 9 are ruled by these 6 royal families today. The black sheep among European royal families are the Bernadottes of Sweden. Becoming royal family only in 1818, they are late arrivals into the European game of thrones.
Despite family ties, European royals have often been at each other’s throats during the history. Perhaps the most drastic example is the Great War. Kaiser Wilhelm II, King George V and Tsar Nicholas II were all descendants of British King George II. That didn’t stop them from starting a war that killed millions. There are several anecdotes describing family gatherings were young Wilhelm have caused havoc, estranging himself from his British cousins, leading to him resenting them. Today, the relationships between royal families are much calmer and disputes are resolved behind the closed doors without involving the public eye.
To keep things simple, we have concentrated on European royal families that hold the throne today, other ways, there would be too many to choose from.