Your DH appears rather dense and overly controlling to me - trying to force you into a mold you are not comfortable with - and have explained this to him numerous times, by the sound of it. He is just sticking his head in the sand and trying to push you into something that will never happen.
You say "It has to stop eventually, right?" tbh, I wouldn't bank on it. If you're putting all your eggs into that basket in terms of your hopes for the relationship, you might want to re-think.

It will never stop. It will continue into his twenty, into weddings, Grand kids, family vacation with SS , SS wife and GK
If you want a child of your own do it, you can afford it. Like everybody else can afford it

My DH tried this early on with my three SS's. He tried to force us to spend time together. I found them to be unruly, entitled bullies who I could barely tolerate. They didn't like being saddled with me while DH was at work. In reality, DH's attempts to push us to bond caused my relationship with my SS's to suffer to the point it will never heal.
I never wanted to be their mom, nor did they want another mom.

DH finally stopped but only after they started refusing to come over. Now he doesn't expect me to do anything for them.
He gets that he was a big part of causing the problem. Sadly it is too late to fix.

I think you and DH might need to go speak to a therapist together and have some serious hard talks.

DH is wanting you to step into a mothering role for his child. As long as he's not trying to get you to take over everything so he doesn't have to be dad I don't feel he's exactly wrong. Many women who date men with children will start to view the child as somewhat theirs. They will develop a type of love for their stepchild. As long as they respect and understand where the boundaries are I don't feel it's wrong or wrong for the biological father to expect.

Now on the other hand some women who date men with children tolerate the idea that they have to share. They have no investment in the child. Sure they play nice but if visitation stopped they wouldn't care. They understand the impact the child has on their partners happiness so they support their partner but don't do anything extra in terms of the child.

I think how much you love your partner's child falls on a spectrum. One end is 'child could disappear for all I care' and the other is 'I wish the child were mine and BM would go away forever'. I'm not saying your at the complete child disappear end but I'd say your closer to it while your DH is expecting you to be closer to the other end. This is only going to cause issues if you guys don't come to an agreement. You'll end up resenting others. You resent him for forcing his child on you and he resents you because 'why don't you just love my child'.

I know my partner wanted me to accept his children fully. I would love for them to come live with us full time. While I understand they have a mom and I won't replace her I like our family when they are home. I miss them when they are gone. My partner expected this of me and if I didn't really care for the kids we might be friends but we wouldn't be trying to build a life together. Basically I know 100% that if I were to act like you he would leave me tomorrow.

And that's ok. It's his right to decide what kind of person he wants to date and have around his kids. What wouldn't be fair is to ignore it and let it impact our relationship to the point we hate each other. It's better to be honest.

You aren't an evil step mom. You just don't care to really even be a step mom. Your fine supporting your partner and in that extent his child but its HIS child. You don't feel you will ever develop a mother like attachment to the kid. Again that's not wrong. It's not for everyone but you and your partner need to come to an agreement. He can't make you love the kid but maybe he wants someone who will.

Just be honest with yourselves. Do you really want to spend a good chunk of your live just waiting for the kid to grow up? Do you want to fight about not being the kids mom? Is this the life you want?

For the most part, men love to push their kids off on women, whether it’s BM, SM, a girlfriend, a co-worker (how many men bring kids into the office and let the female front desk clerk watch them?), and so on. Some men don't want to be bothered; and some just feel uncomfortable with what they see as huggy, kissy, touchy, feely stuff; some don't want to do “women's work”; and some are just a$$es. The list goes on and on.

At the end of the day, it doesn’t really matter what the excuse is. One of the causes of SM burnout is: “Remarried men with children may expect their wives to be more maternal than they were with their children.” And, in reference to SMs, some will even back them up on this—that SM is supposed to be more of a mother to another man’s children than that man is supposed to be a dad to them. Part of the crazy backward world of being a SP.

If only people knew how many SMs go out of their way to get dad and his kids to spend time together, as it should be vs. the usual stereotype of SM magically restraining dad so he can’t be with his kids at all. This has nothing to do with kindness or caring on anyone’s part. DH is trying to push HIS child-rearing responsibilities off on you because it is easier for HIM. It is not easier for you, nor for his children. Continue to just say NO, and mean no. Since it is the year 2017, men need to realize that in the event of a divorce, they need to act like the parent whenever SKs come over vs. trying to dump everything on SM.

Do not ever let him foist it on you. Trust me, it's not worth it.

I am very lucky with SO in this regard. His vision has never included me being a mother figure.
I don't know if that was always his vision after divorce or if that was shaped in part by me being, well, me.
Either way, it puts us on the same page and that's priceless. This whole beautiful mess would not work if we were fundamentally at odds.
I feel for you OP - if SO ever flips the script on me we'll be having some very difficult conversations.

I know you said you guys have had conversations but have you tried rolling it into a discussion about all of the recent change?
Is this new place/move more symbolic to him than perhaps you're aware of and that's triggering something?
His reaction of hurt feelings sounds like something along the lines of dashed hopes. Maybe you can help him re-frame.
Good luck!

I think it's natural for the bio parent to wish their new partner was the other bio parent - especially if the relationship with their ex is not amicable. I also think it's natural to want to have that happy, blended family. However, while it might be natural to feel this way it's not realistic.

My DH often used to say in the early days that he wished the skids were ours and I never responded to that comment as it seemed kinder to say nothing that tell him I didn't wish the same thing. It's very hard to wish someone else's kids were you're own and it's probably hard for the bio parent to accept this.

Misaligned expectations in blended families are very common - counselling really helps to work through them!

My situation is a little the same and a little bit not. DH ex did not teach the children any type of mannerisms. And with that I mean, no thank yous, pleases, no table manners nothing. Then I come along. my DH sees how well behaved my girls are, how polite they are and he is like- you really need to step and be the mother they don't have. I tried it. For a little while. What I didn't see coming was the use of SD becoming "spykid" at 6, and refusing any and all type of love, guidance etc. So I basically decided, with the help of my oldest daughter (yes, I had to ask someone in the house and it wasn't going to be my DH, plus oldest at the time was 18) we just let things fall where they did. I allowed SD and SS to be who they were, and my DH saw first hand just how awful it was. We were at thanksgiving dinner with his family (a very large family) when SD decided she was going to not like something she put in her mouth, so she just spit it out right there on her plate in front of everyone. She did this twice in the course of the dinner. DH just looked at me like it was my fault. I finally had to have a come to jesus and inform him I am not his children's mother. It is not my job to teach them the things they should have been taught from the very beginning. I have my own children and I have taught them from early on, not my problem that his ex was lazy and he became immune to what she wasn't teaching them. And, to make it a bit more sad, I decided to have pity upon these children so I started to engage more with them, and this is when all my problems erupted with SD and SD telling SS "if you listen to what she says, I will hurt you, etc.." SS believed his sister so you see where this is going. Ex's sister is a vulgar woman along with ex's mother, so I had three grown women, bashing me and my girls to the point where my middle girl overheard them talking about me at a sports event for one of the Skids- she turned around and firmly put them in their place- I was then counseled on teaching my child manners. (insert eye roll here) Anyway, what I'm trying to say is, I think most of us have all been there- and it is really a personal choice. I personally gave up on being that mother figure- I tried, and it just wasn't welcomed, so I stopped. my SS however confides in me religiously, he and I have developed a very good relationship despite all of this, and he has, as he has grown older (he's 12 ) viewed me as mother figure in his life, but it took him to come out of his shyness, and decide on his own. Even with that said, I keep my distance, I don't trust the influences he has outside of our home. SD has others thinking for her and telling her what to do for her.

As a mom of three girls, with an ex husband who had 2 that I also raised, I can not fathom the things that BM's do to "get back" at their ex's and the new spouses when children are involved. My ex and I didn't see eye to eye when we split (it was his decision), but I respected that he moved on, and when he remarried and remarried a woman 20 years his junior, it wasn't easy for any of my girls or myself, but I never ever ever stooped to the level that my DH ex has gone to , nor did I ever have my girls "spy", I never bad mouthed her, I simply just told them that they didn't have to like her they just had to be polite. Of course, it was a no-brainer that ex's new wife was not going to be a mother figure..

I always say I have 5 children: my three, and the two my ex had that I raised. (for those who haven't read, my ex's ex wife passed away when they were younger) It is sad, but it is a reality. I don't believe my mind will ever change about my DH's children. I dont' consider myself in the mother role whatsoever.

Similar situation. SD came into my life when I was 25. She was 3. I was a little too helpful when she was younger and DH and his family came to expect me to assume the entire role of mom even though mom was fully in the picture. I should have stood my ground and said NO more often and enjoyed my twenties!

Be firm and upfront with your expectations of both DH and BM. They are responsible to fulfill their roles. "Finish what you start" has always been my motto to all of them. I was not hired to be a mommy, nanny, or personal assistant. I came into relationship to be with my DH.

If you don't, it's causes problems later when you really push back. It created a huge family divide for DHa family and us, who we are now estranged from because of all this.

And none of this really has to do with the kiddo. It has to do with two people who created a human and now cannot figure out what to do.....so they try to dump and replace.

You do what you are comfortable with. Like I always said.....I wasn't in the delivery room!