if she's been dating dude for more than a year, and still keeping her kids away from him, there may be more issues than whose baby she theoretically may (or may not) carry. divorce is hard on kids, and she doesn't have to make him part of their daily life, but no contact at all seems extreme.

and he needs to get over himself a bit - LW is right, it's just like imagining which famous actor one might sleep with. never gonna happen, not reality-based