I've been working on a data-driven project studying royal marriages, and one of the first examples that come to mind is the marriage of a prince and princess from two different countries. But strangely enough I'm finding no such examples between 1400 and 1900 in Europe. Could any of you tell me if this is true or a problem with my code? I'd appreciate any examples!
One famous example was the marriage of Louis XVI to Marie Antoinette, in 1770. Louis XVI was sixteen and the grandson of Louis XV, the sitting king of France. Only one of Louis XV's sons lived until adulthood, but that son died in 1765. Thus, Louis XV's grandson became the crown prince of France.
Marie Antoinette was one of the younger daughters of Maria Theresa, the Empress of Austria, who lived until 1780. Marie Antoinette was only fifteen when she married Louis XVI.
Source: "Lines of Succession: The Heraldic History of the Royal Families of Europe." This book has the family trees of all the royal families of Europe and shows their coats of arms.
What about Catherine of Aragon, daughter of Isabelle of Castile and Ferdinand of Aragon, and Prince Arthur, son of Henry VII and Elizabeth of York?
There are quite a number of examples in Spain. However, the Habsburgs were very keen on intra-family marriage, and it was often the case that both parties were members of the larger Habsburg Empire, so not exactly two separate nations or monarchies - I'm not sure how that would factor into your data. But here are a few from both the Habsburg and Bourbon houses (please note I'm just using the titles Prince and Princess here in their general terms meaning legitimate children of monarchs - exact titling for each person varies, especially by country):
Prince Philip of Spain (the future King Philip II) married Princess Maria Manuela of Portugal in 1543. They were cousins. Their parents, respectively, were King Charles of Spain & Isabella of Portugal (ruled 1516-1556), and King John III of Portugal & Catherine of Austria (ruled 1521-1557).
Princess Maria of Spain (sister of Philip II) married Archduke Maximilian (the future King of Bohemia, Germany, Hungary and Croatia, and Holy Roman Emperor) in 1548. Their parents, respectively, were, King Charles of Spain & Isabella of Portugal (ruled 1516-1556), and King Ferdinand I of Bohemia and Hungary & Anne of Bohemia and Hungary (ruled 1526-1564).
Prince Ferdinand of Spain (future King Ferdinand VI) married Princess Barbara of Portugal in 1729. Their parents, respectively, were, King Philip V of Spain & Maria Luisa of Savoy (ruled 1700-1746), and King John V of Portugal & Maria Anna of Austria (ruled 1706-1750).
A brother/sister match for the previous one: Princess Mariana Victoria of Spain married Prince Joseph of Portugal (future King Joseph I) in 1729. Their parents, respectively, were, King Philip V of Spain & Maria Luisa of Savoy (ruled 1700-1746), and King John V of Portugal & Maria Anna of Austria (ruled 1706-1750).
Another brother of Ferdinand: Prince Charles of Spain (future King Charles III) married Princess Maria Amalia of Saxony in 1738. Their parents, respectively, were King Philip V of Spain & Elisabeth Farnese (ruled 1700-1746), and King Augustus III of Poland & Maria Josepha of Austria (ruled 1734-1763).
Let me know if you want any more info!
(added in dates of rule for clarification, and added a couple more)