Tbh I'm not sure I would enter into a relationship where such strict boundaries like forced monogamy are imposed. It would be clear from the start that so long as they still love me then I wouldn't be particularly bothered with it. You can say that if they cheat that means they don't love you anymore but I say that isn't true; if it was just sex then it was just sex; many many people have casual sex and they don't all love each other like people in a relationship do. Even if it wasn't just sex, who are you to restrict the emotions of someone else? I don't believe love should (or can) be restricted to just one person so to force someone to do that is stupid. Of course, if they stop loving you then you have every right to cease the relationship, but that can happen without any cheating at all. *dons flamesuit*