They think they can change them. And we all know that ain't happening. In General, men don't change. My gf's ex is a cheater... he's cheated on EVERY woman he's been with. Once a cheater, always a cheater. She got hurt so bad she physically had her larynx shutdown on her. She went to all kinds of treatment, acupuncture, steroids, etc. nothing worked, she got some of it back, but it's still raspy. They were going to operate next, and she said enough. She's still got emotional (closeness) issues about it she and I are working thru. She put up a wall around her(normal behavior when you get hurt) that she still won't let anyone in. Hopefully your friend Kate will be smart, and take care of herself and the kids, and kick him out and take him to the cleaners. (I'm usually not wanting that, since my ex did it to me and I wasn't cheating on her, we just had irreconcilable/communic. issues. But this guy needs to have it done to him)