He's right.  So stop doing anything for them.  Don't cook, clean, transport, discipline, babysit, or buy anything for them.

Separate your finances.  If you live together, the housing cost should be split equitably, meaning you share a bedroom with him, and the other bedrooms belong to his children.  So in a three bedroom house, his responsiblity is 1/2 + 1 + 1 = 2.5/3.0 and yours is 0.5/3.0.

Same with food and utilities.

Easy: stop doing anything a mother would do.

And spend some time reflecting on whether your DH is an arse or if you overstepped and he snapped. 

I would feel it's a sign to excuse myself of any responsibility to the kid.

I can tell you once that happens those comments stop.

I have always considered this comment made by your DH and so many in the blended family world as what it is .... complete bullshit.  We are a parent to any kids raised in our home and within our marriage.  

Our title clearly states that we are a parent.  We are a stepPARENT not a StepWife or StepHusband.   PARENT is the operative element of our title and the role we fill for StepKids.

My wife would never think much less say what your DH has said to you.  If I were you I would give him clarity that he is on the ragged edge of homelessness and another divorce if he continues that bullshit perspective.   Then demonstrate how much of a mother you are by stopping all mother and parenting activities in your home and letting him deal with them.  Don't warn him, just stop.  If the kids ask you for anything tell them to talk to their dad.  NO picking up, no feeding, no laundry, no nothing.

Then after DH is freaking out and is hip deep in dirty dishes, laundry, having to leave work to schlep his kids around, has to sit and supervise their homework, etc, etc, etc.... Ask him how much of a parent and mother you are to his chidren.  Do absolutely nothing that will benefit his children in any way.  

Once he is quaking and snivvling about the state of having to parent his children entirely on his own including all support, home making, earning, etc, etc,etc.... , tell him to ask you nicely to re-engage and give him clarity if he ever pulls this "you are not a parent or a mother" crap again he will be completely on his own.

Good luck. 

It's a jerky thing to say - and as the others said, since you aren't their mother and not a parent, you are free to live your life as you please, while he can take care of all parenting (which he should be anyway).

There are worse things than divorce.  I'd rather be divorced than be married to a jerk who doesn't treat me right.

The ONLY reason I am willing to have responsibility for my skids and do the things a MOTHER would do for them is that I also have authority to discipline them, and my efforts are appreciated by both DH and the skids (and also by BM).  

To answer your question, if my DH said that I would feel anger, and I would react to that by disengaging and refusing to do anything for his kids.  He could gaslight me until the cows came home, but fear of divorce would not get me to pick up his slack when my efforts were not appreciated.

Seriously, his next move is going to want you to have a baby. Do NOT get pregnant! 

I would put my shoes on, put my coat on, pick up my bag and walk out the door. Then I would spend a good few hours out of the house and ignore my husband for the duration. Thankfully I have only done this twice in my marriage. It was effective both times. Actions speak louder than words. 

He would have been right of course. I am not the child(s) mother and so I have no need to be there looking after them or picking up after him (an adult). He the "real" parent can do all that sh*t.

Luckily for me my husband sees me as a parental figure in our home and has ensured that my sd does too. I am not her mother, and have never tried to be but I do choose to do a lot of things for my step daughter. He expects her to treat me as a parental figure and be respectful towards me, listen to me and do what I ask of her. 

As my husband's spouse my opinions on issues outside of the home (schooling, medical, custody etc) are always listened to and considered. I know that ultimately it is up to him and BM to make these kinds of decisions though. 

Kelly I am also a sahw whose husband spews this comment when I make the mistake of occasially caring about sd9 well being in making the homeless looking feral child civilized. I have been training my dh to be nice to me by basically doing what Rags states above by giving him clarity of all the motherly things I do for sd9. 
 

When dh says something mean to me or displays an ungrateful attitude towards me I calmly let him know this is not an acceptable way to talk to your wife and immediately stop whatever I am doing for him and either leave the house or go to my room. 
 

Last night I was baking him breakfast tarts for the next day when Sd9 came in for her evening snack. He asked her if she put her laundered clothes away and she said yes. I grilled her a bit more and she caved admitting that she did not put the clothes away. Dh told me to not interrupt the situation next time. I prompltly put my baking in the fridge and went upstairs to read a book. 
 

dh was mad this morning that his tarts were not made. I told them it was his own fault for being rude to me and I don't have to put up with that. 
 

He later text me to apologize and all is well with this training excersise. Rinse. Lather. Repeat as many times as necessary until dh can be nice to you. I promise he will get the hang of it and your training excersises will eventually occur less and less. Alpha men only respect those that have the ability to put them in their place.