Fact of the matter is also that just because you think about it you don't have to act on it. While I have as I said thought about it. I have never acted on it until either One he did it first and then I don't see it as cheating. Or two he made it very clear it is over and he doesn't want to be in the relationship anymore. Thus again if it's over it is also not cheating.

If they are loyal then you have to be loyal back or end it. What a person thinks doesn't have to be acted upon.