Royal intermarriage

Practice of ruling dynasties marrying into other reigning families

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.

From Wikipedia, under CC BY-SA. More on occurri.