Feedback/Opinions

Hello everyone im 26 and my fiancé is 35. We have this argument ever so often if flirting with other women online while your in a committed relationship is considered cheating? No he has never gone out that I know of an slept with anyone while we've been together but I do think flirting with others could possibly lean to that. What are your guys thoughts?

Side note: He doesn't see it as cheating since he is not going on and doing the deed.