@Jahangir. he hasn't done anything wrong YET but there is a chance perhaps, and keeping this from his gf will seem suspicious to her when she eventually finds out. It's like, "if you aren't doing anything wrong, why hide it?" thing. If they had just told her from the start, I'm sure the fml would be okay with it. Hiding things like this when in a relationship is not a good idea, it never is. That being said, it isn't cheating, not per definition atleast. I think what is upsetting people is that he spends time with another woman, without telling is girlfriend.