Fall in love with a french man but..?

I fall in love with a french man that i met in club,unfortunately, i just found out that he has a gf who has been living with him for 10 years..it makes me so sad to find this out :( I mean, I deeply in love with him... on the other side, i feel guilty to his gf. Im a kind of person that hard to like a man, so when i like the man, it will be very deep. Pls help me ..