Being the other woman is a thing I'm going to be.
Being the other woman is a thing, why would you want that?
He used to tell me about his wife and kids, and I don't want to be emotionally involved with someone who has a family outside.
I personally find it a bummer that you have be drawn into this nonsense. You deserve a better partner, one that is loyal to you.
He's weak.
You get that what is happening is wrong and that this man is weak. Move on and and a person who is good and supportive.