In my experience of human society, marriage is extremely transactional. It's modern legal form was invented largely to legally codify how wealth transfers related to marriages would be handled, essentially.

A marriage in today's society is more of a business partnership than anything else; infidelity is as common as not. Often in wealthy circles joint business ownership precludes divorce as well, so enter the side partners. Typical aristocratic nonsense, which is what you get with Empires.