If my DH insisted that I do anything let alone parent his brats, he would get a ride awakening.    You didn’t spawn them, you didn’t create them to be the monsters they are and they don’t respect you. 

Tell your DH when he and BM fix the attitudes and behavior of their spawn you would then consider being in their lives in whatever way you feel comfortable.  Otherwise he can just deal with it. 

A great saying, people treat us how we allow them to treat us.   Your DH will try to force you into raising his spawn with no backing from him because you allow it.  Stand strong and he will have to figure it out.

It is so NOT your job to "fill in as their mother" - they already HAVE one of their own! Not only that but I seriously doubt that your wedding vow adressed anything or anyone other than your relationship and your husband. Right? Bet there wasn't anything about being a mother to his kids, was there?

Tell him to get his ideas straight - he is their father and it is HIS duty and responsibility to raise them to be decent human beings and he is your husband and it is high time he started treating you like a spouse.

Tell DH politely that you are disengaging (if that is your true chosen path).  Tell him that he said you should be their mom yet it sounds like he is not suporting a mom role.  If he did then you two are the adults and the kids need to listen or lose privs, etc.  Now if disengaging is your way to try to make him see the situation and back you then this is your chance to have him put up or shut up.  However, if you are truly done and only want to disngage tell him that if he backed you earlier that may have worked but the situation is now what it is and this is your final answer.

His response was that it was my job to fill in as their mother since I married someone with kids.

It is absolutely not  your job and I would tell him so. He went two years without seeing them at all and now wants to push his responsibilities onto you. NO.

Don't talk to him about disengaging, just do it.

So you married someone with kids, and he just assumes that you HAVE TO play the Mom role? How come HE gets to make the rules about what YOU should do? That's not the way a partnership works, and I would enlighten him about that.

You don't need to try to explain further, just do it. "Ask your dad" all the way home any time the children ask you to do something. If your husband complains tell him that you tried to explain but he chose not to try to understand your point of view or try to find compromises and solutions. If he wants to discuss it then he can make an appointment with a marriage councilor and you two can discuss it with them. I might also be tempted to be at home as little as possible over the next couple of weeks to a month to help him see how much work you do for these children and to help him get into the mode of doing the parenting in your household. 

So now, every time she is noisy in the morning, you wake your DuH and tell him to do something about it ... 

This sounds the same as what I've been struggling with. The men seem to think because we are women we'll just automatically slot in as caregivers of their little darlings. Its bloody hard! I am currently pushing against MiL who had said she would help her son on the weekends he has his 2 young kids... now the novelty has worn off over one year & shes trying to bully me into doing it because apparently I knew he was a package deal when I got together with him. 

Hang in there! 

"(Your) brats are not my responsibility? Especially since they are girls and (you) seem to think I should be doing the lion's share of the work raising them."

Your original comment just about sums it up.

Go with that

His response was that it was my job to fill in as their mother since I married someone with kids.

Your H has some nerve trying to pawn his ill mannered children on you and on top of that doesn't even give you the support you need when you did try to parent them. Good thing you have disengaged and trust me he'll feel what it's like to deal with poorly disciplined kids. You must have the patience of a saint because I would have left his sorry misinformed @ss ALONG time ago. I wish a man would tell me some sh!t like that......

Now you are going go make that right.   It's his kids,  he takes care of them.  You are not the babysitter.  

Hand him the keys to your car and tell him it needs to be gassed up, the oil changed, and vacuumed out.  When he asks what you are talking about, tell him that it is his job since he knew he married a woman with a car.  Your mother needs to be taken to her medical appointment?  You guessed it.  He knew he married a woman with a mother!  Wow, that dental bill you just had?  Guess he needs to pay that since he knew he married a woman with teeth, huh?   

How do you feel about these jobs now pal?  LOL

 be actively involved with them.

i truly got to that point over a year ago, i focus on my 2 kids with hubby, my university studies. Any events even in law ones that skids will be at i refuse to go and play a fake “1 big happy family thing”, my sil’s know that in future if i do not attend family events and skids are there, its because of their serious disrespect, attitude, negative vibes, they actively try to make it feel so negative like I shouldn’t be there with my kids or husband. 

So i’ve focussed on my calm zen kind of place without skids invading it. Yes i married a man with kids and he himself is frustrated with his kids, i mean bio mum alienated all 3 of them, they do not respect others, sd’s actively follow what their stepdad says when he oversteps any authority he doesn’t have and bans them from seeing their dad, they all have a degree of dysfunction courtesy of bio mum and over time its come to light how severe it is.

i told hubby 5 years of tolerating this crap from his kids is 5 years too much and they purely do it because they can and the point of apologizing is long gone. He just needs to respect that there can’t ever be a relationship with his toxic kids ever. People can say forgive and forget but you are past a point of caring sometimes and just want to get on in your world and not deal with their crap.

i truly don’t ever want to spend another holiday with hubbys kids with ex and be reminded of my subordinate place and that me or my kids should not exist and how they actively intend to upset and hurt us... forgive and forget is long past, at that point i just have moved on with my life to not care about them anymore. You reap what you sew.

if you foster good relations and model good behaviour, you get that back, but when you foster and actively  encourage hostile relations and thrive on that manipulative power, people don’t want to be aroynd you, there is no poor pity me card.

even my husband claims his adult son is sorry and wants to ask for forgiveness because it hit him how alone he is going to be during holidays because i have refused to be present with my kids and subjected to tolerate his shitty behaviour, i was done wanting anything to do with him over a year ago

when my husband said his kids loved me as a mummy, i pretty much asked him sarcastically what pipe he’d been smoking as their behaviour clearly showed that me and our 2 kids should never have existed in the first place. You really struggle to get past that resentment and when you’ve been let down continually, you have every right to disengage

He wants you to play a role but him and their actual mother won't?