I really feel I need some perspective here, so any replies welcome. Have name-changed as my cousins and sister are on MN alot and might recognise me.
The problem I'm struggling with is regarding my DP's relationship with my DD.
A bit of Background : Was a single parent to DD when I met DP (she was 1, is now 5). Took my time before introducing them, but when I did they got on fine. Even when we moved to a new home (together) they got on fine. DD has never seen her biological father (I have tried but he's not interested).
Fast forward to now:
We now have a DS together (1) and we all live together supposedly as a 'family'. However since DS was born I have noticed changes in the effort DP puts into his relationship with DD.
Things he does do for/with DD
Will take her to school in the mornings when I'm working but (in his words) "doesn't want to pick her up in the afternoon unless I really have to as pushing the buggy up the hill is hard work"
Helps her with Homework
Baths her
Cooks her nice dinners
Talks to her , answers her etc
Cuddles her
Things he does with DS I noticed he doesn't do with DD
Actively plays with DS, but not really with DD
Will take DS out to park / his friends/ shops etc but won't take DD unless he absolutely has to (ie - I'm away)
I have noticed this for ages but didn't say anything (thought the playing thing in particular was just because DS is a boy and likes rough and tumble play) until one day when I asked him to pick DD up from school instead of taking her and he was reluctant to do it (buggy up hill thing) - I said I don't think that's really what it's about and he should have completely equal responsibility with me. He said "ultimately picking up (DD) is not my responsibility"
I was

and we had a discussion about it later on, which basically came to this conclusion:
Before we decided to move in together and have DS we spoke at length about how it would work with regards to DD.DP at the time reassured me that he "would never make a difference" between them. I thought this meant we would take equal responsibility for parenting them both. He thought this meant that the children wouldn't be treated differently at all and he would help out with her but DD would continue to be my responsibility ultimately.
So we really were never on the same page!
He said he thinks he does a lot for her (he does) and he finds it a struggle (wouldn't elaborate on why other than he feels like a bit of a fraud and that 'DD's dad could waltz back in and I would be forgotten about') and he gives as much as he can but if I'm looking for any more than the current situation then he can't give it
, and he is 'fond' of DD and cares for her but can never love her(although he won't show it) or take the same role as a biological parent could. I think he should take the same role as a biological parent. So we are at a stalemate and I'm wondering if this can be resolved or we are doomed to split?
Sorry about the novel-length post but thoughts welcome 