On BS12 since he is too scared to parent SD brat.  DS7 is going to see the double standard on how H treats his princess.

Are you using a crate for the puppy - especially overnight? It will make housebreaking so much easier.

i understand your frustration with DH not treating the kids the same. I don't think he should discipline your son at all, but the two of you need to figure that out.

But, I thought you were going to disengage from SD? Don't worry if DH has talked to her or not. Only worry about her if and when she actually shows up at your house. Outside of that, don't give her, or her relationship with DH, any thought. It is on him to handle it.

Unfortunately if you drag his daughter into this scenario (she had nothing to do with the puppy peeing everywhere) then he will just double down on his stance. 
 

You may want to clarify with him that he can address his concerns with you then you address them with your son since you seem to not be okay with his level of authority 

Also sometimes some men are a little more tougher on the boys than they are on the girls. Not saying it's okay but just a possible explanation of why he goes hard on them but soft on his daughter.

And why would he make a 12 year old buy paper towels like he can just go report to a job on Tuesday and use a paycheck to buy said towels? Most 12 year old boys haven't developed a work ethic to get side hustles like that.  An 15/16 year old boy yes but not a 12 year old. 
 

I think your husband just mad because he doesn't know how to train a puppy. Which is a hit to his masculinity. So he's taking it out on your son and if your son is unfazed he's taking it out on y'all's other son. 

Hey, JustanotherSM17,

Your post brought back nasty memories of my own home life with ex-husband #2. I had two daughters from my first, disastrous teen marriage and #2 and I had a son together. Much like your experience, our son was gold whereas my daughters could do nothing right. Certainly, all parents tend to view their children through rose-coloured glasses but my girls had been strictly raised by necessity; I left their psychopathic dad when they were very young. 

My daughters were ‘A’ students, gifted athletes, worked paying jobs from the time that they were each 14 years old and performed numerous household chores. Additionally, they were respectful to their stepfather because I would not have accepted anything less. The stress of hearing constant criticism towards my daughters, the anxiety that the girls and I suffered, walking on eggshells while waiting for the next loud, undeserved reproach, became intolerable. 

I could see the girls become gradually beaten down by always being in the wrong and, although I begged my ex to let me do the disciplining, he refused to change. Not until I began to despise him so thoroughly that I filed for divorce. Then, he promised to do better! Talk about too little too late. I couldn’t even look at the man without wanting to punch him in his spiteful face!

 Hon, the worst part of the whole situation was that my daughters loved their stepfather and tried their best to comply with his unjust and ridiculous requirements, none of which applied to our son. I can guarantee that you’ll begin to resent your husband as thoroughly as I resented mine. My ex had a lot of good qualities; otherwise, I would not have married him. Had he not been so awful to my older children, I’d still be with him. However, since I’m now hitched to the man of my dreams…

It's a fact of life that people are more annoyed by the faults of others' children than their own (and no kid is perfect.) But, to live with others' children you really must realize that. If your DH is so blind to his bias that his behavior has you considering leaving, maybe marriage counseling could help? Since you have kids together, it's worth a try. You don't want your kids living with a man who treats them badly, but if you split up, you won't know how your mutual kids are treated when with him and any future SM. It's a tough situation and one you shouldn't put up with. Hopefully counseling will help. 

"You will not speak to either of MY children about anything behavior related until you give me a recorded conversation you have chewing your failed family progeny's idiot ass. Not one word. If you make the mistake of not hearing and complying with this, pack your shit and get your CS checkbook ready because I will have you living in a refrigerator box under hte local overpass. Do not test me on this. Man up and deal with  your shit spawn... or be gone. Your call. Until you play that recording for me, get your ass out of bed and take the puppy out or clean up the puppy piss yourself.  Happy New Year!!!!"

person is mad over there so he lashes out over here. That is my life the past ten years.

If you are thinking that it will get better. It will not get better.

I see this unbalanced behavior so much.   So often these men will treat their own subsequent bio children they've had with a second wife more like they are a step child and not a bio child and the bio child they had with the first wife is treated a lot differently.   Awful.   

He should not be disciplining your birth son.   Unfortunately it sounds like the puppy is an added stressor to the situation.   A 12 y.o. really can't be fully responsible for a puppy.  Your DH needs to back off of your bio son.

You have two young children with this guy.  You have huge leverage. So, put your foot up his ass, get the papers ready, and inform him that if he fails to do as you tell him when you tell him he will be paying CS on two for the better part of 20yrs and he will rue the day he failed you as a viable mate and failed your children.

I am not particularly forgiving of this kind of crap and therapy far more often than not.... is just a delaying distraction.  

It was for my XW and I.  Though it was a God send for me, it sustained a failed marriage for about 6months longer than it would have otherwise lasted. Though that 6mos was likely far less contentious than would have been the case if he had not gone to therapy.  Divorce was filed within a couple of months of XW walking out of what turned out to be our final couples therapy session. The divorce was final 7mos after that session.

According to some research, approximately 38% of couples who have undergone marriage counseling get divorced within four years after completing the therapy sessions.Mar 7, 2022

Some marriages just work for whatever reason.  Some have zero chance from the beginning.  Probably my only regret in life is that I did not end my first marriage with an annulment on Monday AM after the horror show of a reception and wedding night on the Sat before.

So far in my life I have had both.  The first had zero chance. Though nothing is guaranteed, this one is looking good so far.

He taking it out unfairly on your DS Because he there like a punching bag.   Tell him not to tell your son nothing.  Wnen you buy a pupply. It's the adults who has to take care of said puppy. Not a 12 yo.