I can only talk about my own expereince, but i never went looking for or expecting anything I just feel (Soulmate and me both do) it was fate and meant to happen. Even when we went out the 2nd time, it was just to talk about what had happened, with no expectations. I'm certain it won't happen to me again although perhaps I am trying to convince myself there is a difference between a once scenrio that resulted in love with the person I should be with and repeat 'offenders'. History is a good basis for future behaviour, but.....
If it helps you, I think there is a big difference if he has totally split from his wife and there is no chance of him going back 'for his kids'. If he didn't love his wife I can really understand why he stayed for the children. If he has made that break I think things are much more positive for you.
I'd express your concerns to him. Hope it all works out!