Though this is not an example to emulate for lots of reasons, it's worth pointing out that in French culture, until just a generation or two ago, men were not only expected to be sexually unfaithful to their wives, social customs existed that formalized and normalized the taking of a mistress.

If a man could afford it, putting a mistress up in a nice apartment, and going out with her sometimes in public, was a mark of status.

He was expected not to embarrass his wife by violating certain unwritten rules, but so long as he followed them, his pair bond with his wife would not be in danger.

French women of just a generation ago quite understandably reviled this custom and demanded it end. But it wasn't the sexual infidelity that enraged them. It was the sexism of it. Because if a married French woman were caught having an affair with a man who was not her husband, all hell could break loose and her life would be destroyed.

French women demanded equality, but not necessarily sexual exclusivity. Today, French men who try to keep mistresses in the old way are often scorned.

But ... French people in general remain less likely than Brits or Americans to value strict fidelity within marriage. I don't think the French have it quite figured out yet, but I do think they understand that pair bonding does not necessarily demand strict fidelity.

Which, as I mentioned in another comment here, gay men also seem to have figured out.