Sounds like everyone needs discipline, including the dog.  I can't imagine dealing with 4 stepkids 12 and under.  I would have run straight for the hills.

You are not alone and your H brushing your feelings under the rug is not good. If he doesn't address his kids about your personal belongings I would. I'd tell all 4 that they are not to touch your couch, charger, or blanket and if they do _______________ (fill in the blank). Take away phones, no tv, whatever. If your H has a problem with it tell him to do something about it and stop ignorning your simple requests. This is your home and your property and they need to learn how to repect it. It boggles my mind when parents say "they have to adjust to the new rules". There is nothing to adjusting but just listening and doing as you are asked. Its not brain surgery and its not complicated. Your H is just giving them excuses as to why they keep doing the very thing you told them NOT to do 100 times.

I'm not sure I have any helpful advice, other than continue to remind them what the rules are, and that you mean it, and get your damn DH to back you up. Or better yet, get him to be the one enforcing the rules.

As for the blanket thing- I totally get this! lol. I actually just talked to SD9 about it the past 2 nights. When I moved in, I brought a blanket with me. It's my favorite, I love it. SD uses it EVERY night on the couch, even in summer when it's hot. And her feet stink, sometimes she stinks until we make her shower, and I've witnessed her picking her nose many times. So do I want her using it? Nope. If I want to use it, she always has it. Sometimes we share, but the other night I kind of jokingly said, stop stealing my blanket! She said, MY blanket! I said, actually, that is 100% my blanket, I bought it and brought it here from my last house. Sooo.... She said, Well it's in OUR house, so it's not your blanket anymore. As in, it isn't MY house, it's their house. Ok, I love SD, but this line of thinking is not going to fly by me. First of all, I live here too now- it's no longer just YOUR house. Sorry kid. She isn't trying to be mean, she thinks she's being funny. But I said, I love that blanket, I would like to use it sometimes too. So last night she was using it, and then actually grabbed the other blanket and used that instead so I could have mine. Yes it seems petty, but it's hard and frustrating to just have to give up some things and be expected to share with skids that you didn't birth and don't feel that unconditional love for. So I get it!

I have asked repeatedly that they not sit in my seat, not because I'm pretty like that

Your typo make me laugh out loud!

I hear a lot about the guilty/permissive parenting but these parents just don't realize that it's not the way to parent. Not in an intact family and not in the case of divorce. Children need the discipline and the structure, even more in a divorce situation.

Kids learn at a VERY young age that there are different rules in different homes and situations, that is a bullshit excuse. They know very well where they can get away with what.

I remember when my niece was very young (had just started walking), she would only drink milk or chocolate milk if it was heated up. Or, so DH and I thought. When over at my dad's and his wife's house, his wife gave her some milk, right out of the fridge, without warming it up, and she just took it and drank it as if that was the way she always drank it. She just knew that DH and I were suckers! If we gave her cold milk at our house, she gave it right back and pointed at the microwave.

Not quite what you are talking about but I always think of that when people say kids can't adjust to different rules between households. Oh, yes they can. They are pretty smart. But, if nobody holds them accountable, of course they are going see what they can get away with.

Also, he needs to teach them to respect other people's property and to respect adults, period. If you don't want them sitting in your seat, they need to respect that.

No I don't think you're being petty. Its about entitled children thinking they can do what they want knowing they won't be held accountable because daddy just brushes it off. When the kids see your H dismissing your requests......it only teaches them to not listen to what you say and they can get away with it with no consequences.

Bullshit their confused. Your DH is a failed placating parental idiot. Sure they're "good" kids in that they haven't killed anyone, aren't doing drugs and get good grades. What they are is manipulative little crotch droppings and your DH is the chief facilitator of their crap. If doing what they should be doing is waht makes a kid a good kid then the entire household parental model has failed.  Good kids don't just do what hey should do. Good kids are comprehensively exemplary.  Average kids are... well... average. Crappy kids don't meet the requirements of the program.  Grades and  drugs are only part of what good kids do not do.  More importantly to what they are not doing is what they are doing. 

Lets assume for a minute that they are confused. It doesn't matter. What matters is that they are know damned good and well what they should and should not do in  your home yet they choose to violate those requirements.

So, punish them.  Make their existence in your home one of abject misery until they comply.

Zero tolerance works. Pain changes behavior.  Bring the pain.

Your husband is making pathetic excuses for his kids.  My SO's kids are 3 and 6.  They were 1 and 3 when their parents separated.  They quickly figured out that Mommy's house and Daddy's house had different rules and different schedules.  They adapted.  They're able to follow the rules at both (most of the time) and at neither household do they get away with bad behavior.  It is ludicrous for your husband to say that kids who are 6, 8, 12 and 13 can't figure out the rules at your house and are "confused."  More likely your husband is confused about who the adults are in your household, and what parenting entails.  I think you have to make it more painful for him to NOT parent his children than it is to enforce the rules and impose consequences.  But in the meantime, don't fall for his bullshit.  This is a case of guilty daddy failure to parent, not of confusion.

Oh, and to answer your question . . . why doesn't he get it?  Because he doesn't WANT to get it.

I've had this conversation with my DH more than once based on several "arguments" for allowing them to do whatever they want.

#1 "It's too confusing to have different rules here than at BMs" If that's so, are they allowed to sit wherever they want, eat anyone else's food, and choose which classes to attend and what homework to complete at school? Every teacher has said they are doing fine and each teacher has different rules. Can they do whatever they want in their sporting events? They know how to be compliant to different sets of rules.

#2 "BM has a lot fewer rules." That's her decision. If she still rules this house then you should never have gotten divorced. I didn't marry BM, I'm not BM, this house will be different. And I know the inference is they will want to stay there more. Fine, if they cannot be civil human beings then they should stay there. Do you want them to be spoiled little kids or raise responsible adults?

#3 "But this is their house." They live here. I am the other adult and parental-figure in the house, they are not. Even if they want to consider it "their house" they don't get to consider the contents of the house as "theirs." If that's so, then I should get to take whatever I want of theirs, whenever I want, too.

These are all met with "but..." and I ask what is incorrect or unfair about what I said. I get the frustration with them being given free range (it's why I resent having to keep anything of value in my locked closet). And I have a child, too, same age range as the skids who does not touch other's stuff and follows the house rules (most of the time) so I know it can be done.