Turns out that friend's partner has been taking the child to meet my friend and all of her family.
I think that is crossing the line a bit. Obviously it's a bit unreasonable to expect no contact with the new partner, but going off to visit her relatives is a bit off.
It's difficult to put into words but there's something about this, as if they're doing the "happy family" act, all cosy together as if baby's mother doesn't exist. I cannot imagine taking a partner's child to visit my family when the child was still a baby. I suppose it might happen unintentionally - are we talking family days out "to meet the baby" or just days when the dad has custody overlapping with visiting relatives or relatives nearby who pop in?
When they first got together he had just found out his ex-girlfriend was pregnant.
The ex has always been jealous and hates my friend.
Hard to judge without knowing the relationship. I had an ex who's ex from before me was really horrible. He turned out to be abusive, and probably still stringing her along when we started seeing each other/at points in our relationship, so I've a lot more sympathy with her now. His next girlfriend thought I was mad bitch from hell! (Then he did the same to her, rinse and repeat.)
When did he find out his ex was pregnant? I'd be a bit peeved if I found out I was pregnant, told ex asap (ie. within a month or two of splitting up) and he was already starting up a relationship with someone else. If they then went aroud with my baby, being a little family without me (they've only been together a year or so!) it would really hurt. She's just gone through the life changing experience of having a baby, alone! I'd feel like I was just the workhorse who had to go through pregnancy and birth and all the hard bits, only to hand my baby over for others to do the fun, cute family stuff.
A lot depends on how it's done...