It's interesting to look at how interrelated the royal families of Europe still are today. Queen Margarethe and King Carl Gustaf of Sweden are first cousins. Her sister is the "queen" of Greece. The "king" of Greece's sister is the former queen of Spain (the current king's mother). The king of Norway and the former king of Belgium (Mathilde's FiL) are cousins.
And that's even before you go further back and discover that most of the European monarchs are descended from either queen Victoria, king Christian of Denmark or both! I think the only exceptions are the Monegasque and Dutch monarchs.