He doesn't "forget." He just doesn't care. He IS lazy. I would "remind" him of every mess every time until he "remembers." And they wonder why we "nag"...

Everyone should do their own sheets (but IMHO, an every other weekend kid need do them once a month ).    Everyone needs to share in unloading D/w.  Get  him to agree to a schedule.  

Just curious, are you paying a share for the house?  he may think sharing should be shares and money.

I would set a standard for everyone in the home.  You make your bed in the morning before leaving the house.. period.  

Their sheets don't need to be washed but once a month.. based upon thier only being in the home a few nights a month.

Logistically, it is difficult to probably expect them to manage the stripping.. washing .. drying and remaking in the short time they are in the home.. and you may even prefer they not mess around in your laundry.  So.. you could do this for them once a month.. or ask their father to do it for them..

Now, as to chores etc.. there is nothing wrong with saying " hey DD and SD... can you come help me for a minute in the kitchen".. then have one unload the dishwasher while the other does some other task.

While they may not be there long enough to have huge responsibilities in a home they don't live in the majority of the time.. there should be an expectation that they clean up after themselves.

I had the same issue with dh. I phrased my statement like this, “sd is going to have a husband one day that she has to clean up after so we should teach her to do that, right?” Dh thought about it and said yes that enjoys me picking up after him and wants sd to be able to pick up after her husband if need be. I would phrase it like that. Now when I tell dh that the bed needs to be washed and what sd needs to tidy up he makes her do it right away. 

OP, if you want things to change, you must change yourself.

Your SO doesn't clean because he knows you'll cave and do it. It's a non issue for him. Men just want to be comfortable, so if you want things to change, inconvenience him. No clean plates or silverware? No groceries for the weekend and the garbage is overflowing? Oh well. Start taking your daughter out for a full day of errands and activities, and leave your SDs to their dad. Don't come home until after dinner. Make sure your daughter's room and your personal space is spotless, and make sure your SO sees your daughter cleaning, doing her own laundry, etc. You've got to outlast him if you want him to change.

My DH just doesn't care about this stuff.  He's great in many ways, but mess doesn't bother him. 

I never touched SS's room at all.  He had clothes all over the floor and washed his sheets every 6 months or so, when I told DH it hadn't been done for a while and DH made him do it.  Who cares? Close the door. 

DH would do dishes after a few days if I left them there, but I can't stand that, so I just do them myself.  He does all the outside work and all the house renovation, so it's not like he does nothing.  He's just not a cleaner so if I want things tidy I have to do it myself. 

I try to get SD13 to wash herself and her own stuff, and DH doesnt seem to care unless her room is super messy.

I do not ever allow eating of food in rooms and just recently banned ice cream. I got a huffy teen but also told her how much I appreciate her respecting our home which is also her home.

Its easier for us because we have 50/50. Every other weekend is hard, because then its "I dont want to bother with the mundane when we never see each other".

I learned the following after a horrid experience...my blogs cover the backgound...I learned:

* To shut a skids bedroom door and leave it.

* And to learn, that if things got too stinky in bedroom (i.e. shut door, could still smell the rot walking by), it's really the adults in charge and that trash bags hold a LOT of things that go away and that I do not replace.

* To not worry about their laundry, ever, after teaching them how to use machines and posting instructions on the cupboards.

* To deal with ANYTHING left out after 24 hours in the common areas; I got to choose what to do w/it because apparently, no one else cares.

* To use disposable dishes/utensils/cups because no one did dishes.

* To not cook because the kitchen was too messy to make something, the sink was full, or all the pots/pans/knives were dirty.

* To clean dishes left in sink after 24 hours, like if I WANTED to cook something, dry them and promptly put them into my special donation bin (a real one - to take to our local place for others to use).

This turned out to be one of the biggest issues in my entire marriage.  It got so bad with my two SS's that after trying and trying with my DW, I gave up.  When I did so (won't bore ya'll it is in my blog), it cause me to become stuck and fixated at a point in time and caused increasingly unproductive and nasty arguments between us.  SS23 is now very successful with his family and no worries.  SS28 is doing ok, gainfully employed and does pay rent.  He bacame a focues of my ire fore 2 reasons.  One being a slob (last time he cleaned his room it took 6 full sized trash bags and the other because though we do not see him all the time I would like him to be successful and visit often and let us do our thing. 

Not reaching common ground with my DW left me feeling deserted and powerless in my home.  As a result we have had about 4 years of at least once a month arguments and no headway to show for it ... SS28 is actually a pretty nice guy other than prone to snap and growl and every so often he does offer to cook, etc.  Because we never reached common ground earlier, we are now rebuilding from scorched earth and still do not have a clear agreement where things are going.  It will be a long road with plenty of work for each of us

Yeah no I wouldn't be happy with this either. Whilst yes it's his kids, his rules. There needs to be a middle ground, a level of fair expectation for all children in the household. 

The door to my stepdaughters room remains closed when shes not here. On the Wednesday following her weekend with us her dad will have her tidy her room up. We have a cleaner that comes every 14 days. If her floor is clear then the cleaner will clean her room but if shes not tidied up then she has to do it herself. 

Bedding is usually changed by our cleaner. 

If your BF is so adamant that they dont need to lift a finger either he needs to clean up after them or he needs to dig in his pocket and pay someone else to.

So, what I get out of your dilemma is that you are sacrificing your quality as a parent to your 11yo to align with your SOs shitty parenting model.

As for the shit storm of a mess your SD's  and SO leave... don't do a thing with it other than pile it all in their bedrooms to fester into a stinky mess behind closed doors until their next visit.  When they open the door(s) to their festering garbage pile and freak out.... tell daddy that he needs to ether man up and deal with their mess or man up and parent.  

Lather, rinse, repeat.  

Anything they soil and either they or he do not deal with goes in the SD's rooms.  You and your DD keep your stuff in order.  Put a lock on the pantry and keep paper plates, cups, and utensils there for the use of you and your DD because eventually there will be no clean dishes due to SO and his toxic spawn.  

Eventually they will be overcome by the stench of their nasty crap and will deal with it... or not. In which case it will remain behind closed doors in the SD's rooms.

Stick to your guns.

Don't let them take advantage of you.  Don't let their crap bother you other than to close it up in their rooms.  Put plug in air fresheners in their rooms and in the hall outside of their rooms.  Put toxic waste stickers on their doors.

Have fun!