Maybe if relationship ever went that far seemed something that would work then why not, but I don't really know to be honest. That depends on woman and stuff... But I would at least question her current relationship with real-father and something about their past. People are not usually emotionally very stable after break-ups and I don't feel like ending up being used as revenge toy, broke-up therapist for a woman until she gets past her ex-boyfriend and decides to move on to other men or when she decides to return back to her ex-boyfriend etc. Also depending a bit from age of kid, that would still feel bit strange situation for me and it is most likely going affect relationship way or another. I suppose older the men are more likely to accept woman having kids as single markets and situations there tend to be slightly different and kids might even be already old enough to not affect relationship anyway... I started to think this for a moment and variables of such relationship, only leading me to more complicated variables, until I started to get headache and gave up... Ignorance is bliss they say...