I can understand where all of you guys are coming from and the thought of my husband falling in love with someone else after 13 years is pretty scary but look at the situation from the guys point of view. He didn't choose to feel that way about this other woman. Offcourse i am sure he was doing things such as talking to na-mehram on the phone while being married which offcourse all of you guys think is okay to do because a guy and a girl can be just friends. But this is the result of those things which we consider "halal" in todays society. And its too late for what he shouldn't have done, it sounds like he has made up his mind about marrying this other woman. And how come no one pointed any finger towards this other woman whoes wrecked a home? I think he did the right thing by telling her. He is way better than ba$tards who cheat on their wives and actually marry these women and think that its okay to lie to your wife about it. Your cousin has two options, either let him have a second wife or leave him. She has to think about the kids(i dont have any so i cant tell you what else comes with that). Most importantly, she has to consider herself. Is she going to be happy with a divorce? Can she go through a lifestyle where she has to share her husband? I am sure he will help out with kids if he is making her part of the decision. Can she support her self financially and emotionally? What kind of support will she get from her family and friends? And offcourse shes gonna have to consider re-marrying, but thats later.
I think any women in this world is much better off with a divorce, than being with a man that is with another women. Also emotionally financially she should be able to support herself. Accepting another woman in her husbands life would take a lot more out of her emotionally than just letting go.