I suppose that depends on whether or not the guy still wants to have a relationship with that kid. If you immediately found out, I could see not wanting to have any relationship. But after years of believing you were the father, I'm not sure how you could just throw away that relationship. So it does help in that way. She can't not allow you to see them so long as you pay the child support.
In the case I saw, he knew it was't his kid right away, and left his wife immediately, the divorce just wasn't final for 2 years.