> marriage is a covenant

That's a very narrow view that's a function of one's religion, culture, and values.

When I was in school, (US) my very Catholic French teacher explained that his uncle, in France, had a mistress. His uncle's wife knew and was okay with it. What my teacher was explaining is that the culture around marriage varies considerably through the world, and you can't take for granted that what we were taught (monogamy) is the standard that others live to, or even expect from you.