Royal intermarriage

Royal intermarriage is the practice of members of ruling dynasties marrying into other reigning families. It was more commonly done in the past as part of strategic diplomacy for national interest. Although sometimes enforced by legal requirement on persons of royal birth, more often it has been a matter of political policy or tradition in monarchies.

In Europe, the practice was most prevalent from the medieval era until the outbreak of World War I, but evidence of intermarriage between royal dynasties in other parts of the world can be found as far back as the Late Bronze Age.^[1] Monarchs were often in pursuit of national and international aggrandisement on behalf of themselves and their dynasties,^[2] thus bonds of kinship tended to promote or restrain aggression.^[3] Marriage between dynasties could serve to initiate, reinforce or guarantee peace between nations. Alternatively, kinship by marriage could secure an alliance between two dynasties which sought to reduce the sense of threat from or to initiate aggression against the realm of a third dynasty.^[3] It could also enhance the prospect of territorial acquisition for a dynasty by procuring legal claim to a foreign throne, or portions of its realm (e.g., colonies), through inheritance from an heiress whenever a monarch failed to leave an undisputed male heir.

In parts of Europe, royalty continued to regularly marry into the families of their greatest vassals as late as the 16th century. More recently, they have tended to marry internationally. In other parts of the world royal intermarriage was less prevalent and the number of instances varied over time, depending on the culture and foreign policy of the era.