The only person that can answer this question is the BPD themselves, but I don't think they can. I remember watching my ex interact with her son (before i knew what BPD was) and it being a really weird. I would often ask myself "does she even love him?"
I started to think that about mine with our two little kids in the past year when our relationship stayed to go downhill. hatred myself for thinking it. based on what I observed and a few very telling fb posts ( as well as stuff I've found she's written), they are the only thing keeping her on this planet. very, very sad. it's a form of love, but what a burden to place on babies! they might feel the truth as they get older... .