intermarry

To marry a member of another group, social stratum, or religion.

Mary was Catholic and Ron was Jewish, but they decided that it was acceptable to intermarry.

The state where most intermarriages took place was Hawaii, where more than four in 10 newlyweds (42.4%) were intermarried.

To marry within the same ethnic, social, or family group.

Mainland China and Taiwan do not border each other by land; they face each other across a 140-km-wide ocean strait. Taiwan-held Dadan Island sits 2 km away from Xiamen. Xiamenese can use binoculars to observe their kinfolk on Dadan Island, with whom they have traditionally intermarried (Mellor, 1993).

Did European royals sometimes intermarry? Yes. There are a couple of examples of that. The Habsburgs are not beating the allegations.