Clear cut rule.. parental room is off limits..you must knock AND recieve permission to enter.  put a lock on the door if you need to.

2nd.. since the kids can't manage to not get into your personal things like tooth brush.. put it away.  I know.. not super convenient.. but she could be scrubbing the toilet with it.. just protect yourself.

3rd.. when messes are found.. dad needs to make them clean it up. period.

If he is too busy to parent.. maybe he is too busy to exercise visitation.. these aren't your kids.. they are there to see him.. make him step up.. or reconsider that you may have not picked a good partner.

Wait until these issues resolve BEFORE moving in. If your BF can't control/parent his kids now, what would make you think it would be any different when you move in? This sounds miserable to me. 

Also, have you discussed financials? I really hope you won't be paying half for everything if you do in fact move in. Set those expectations too. He should pay majority of water, electric, groceries, etc. since he has 3 kids. 

I say this because I learned the HARD way. When DH and I first moved in together, he assumed I would help buy SD all of her favorite snacks, lunch items, etc. I did for a while, but then saw the same food would come home in her lunchbox and just threw food away. Totally wasted. NOPE. We had a conversation about it and I was done buying groceries after that. 

That is a LOT of issues to deal with....and many are serious. You don't "deal" with that after the fact. You get those issues settled BEFORE you move in and get yourself "locked" into an unhealthy situation. 

Seriously, you cannot imagine the strain this will put on your relationship if you deal with this "after the fact." You are one of the lucky ones...asking questions beforehand...unlike many of us who were clueless to the toxic step world and got blindsided by this mess. Please...if you want to stay mentally healthy and you want a healthy relationship with your SO, you really should settle these matters now. 

Best to you.

There is no way I'd move into this chaos at this point.  It's concerning that your bf has already dismissed some of your valid concerns as being "what happens in a house with boys."  It only happens in a house with boys if the parents allow it.  It sounds like he's turning the typical "you don't know because you don't have kids" into "you don't know because you only have a girl," in order to dismiss your opinions.  Not acceptable.

I'd let him know the changes that need to be made before you move in and wait to see what happens.  When I was first dating my husband,  I told him there was no way I'd stay overnight because he had his two daughters sleeping in the bed with him.  He had those kids sleeping in their own room within a week. I knew then that he'd take my concerns seriously.  If changes aren't quickly implemented, you'll know you dodged a bullet.  If they are,  you can see if they last and reconsider moving in.  

Finally, don't let a morality clause in his CO dictate what you do or rush you into something you're not ready for. 

Id suggest waiting a bit until some issues are resolved.

If BM is high conflict now, just wait until you move in.

Try not to fall into the "they really need me" trap. They have 2 parents...dont forget!

Welcome to steptalk.

Here's a list of signs of a Disneyland Dad (copied from another post). You mention that the kids don't have much structure in either of their homes. I would not move in with this guy unless and until you've had some very, very frank and lengthy discussions. Even then, I would hold off and make sure your SO's actions match his words. Ask me how I know. Personally, I would say to run fast and run far. 

1. Does your man allow co-sleeping with his children? (aka the kiddies routinely jump into bed with him at night)

2. Does he have to lie down with them to get them to sleep?

3. Do the children seem somehow "stunted" socially? Do they have poor hygiene habits, eating habits, bedtime habits?

4. Does your man subscribe to the "one big happy family" model? (expects you to love his children as much as or more than him)

5. Does your man have the "inability" to say no to his children?

6. Do his children seem overly "hyperactive" to you?

7. Does your man say "just relax; you worry too much" or "Everything will be just fine" if you bring up a legitimate concern

8. Do the children seem "overly needy" demanding that dad spend 24/7 with them? Do they physically lay all over him and go bonkers when daddy steps out of their peripheral vision?

9. Are they unable to do age appropriate tasks or want dad to do things that could easily be done themselves?

10. Does dad seem overprotective of his children; unwilling to let them try things out on their own?

11. Has dad said things like "I don't want to make waves with the BM b/c it will affect the children" or "we'll take the high road" when faced with blatant BM stepping over boundaries.

12. Has dad said things to you like "you don't like my children" or "my children are UNCOMFORTABLE with you" or "you're a child hater" or "my children are afraid of you" or "my children don't like you?" This is code for you are able to see through the manipulation and the children don't like it. . . and frankly he doesn't like the fact that you can see through his children's manipulation either. He'd rather look the other way as opposed to actually parenting because he might "lose" his children to the (almost always) PASinator BM.

If you can answer YES to ANY of these questions, get your sneakers ready to go.

You can be in a happy healthy committed relationship and not have to live with the guy.  This whole post has planted so many red flags it looks like a poppy field.

Just to add -- My DH actually recognizes problems with SS13 and tries to address them. He does not expect me to parent his child. I'm there to help and advise. BM is not high-conflict. Even then, it's hard. If it's hard under those relatively ideal circumstances, just imagine...

KISS.  Locks and web cams.  Lock every door you do not want the spawn opening.  Inform BF that this is a non negotiable prior to you moving in.

What you describe is a shit show of monumental proportions. So far, you have only seen a peek at the previews.

Start putting nail biting deterant on your toothbrush before you leave after a visit.  SD will never touch your tooth brush again.  Don't forget to rinse it well before you use it. It won't hurt her, it tastes like shit.

If no one is using your toothbrush, no nasty tastes.

If you follow through with moving in with him, make sure you have clearly defined  standards of treatment and the standards of behavior and standards of performance you will hold your Skids and your mate to.  Failing to do that ground work, you might as well just circle a random date on the calendar for the end of the relationship.  The earlier the better for you.

Take care of you.

"What you describe is a shit show of monumental proportions. So far, you have only seen a peek at the previews."

Yeah. It's a big hill to climb. About 9 months into my current relationship, my SO pushed hard for us to move in together. Due to similar issues, i decided to wait. I'm so glad i did. Now i plan to wait until all kids are launched before taking any next steps. You have raised a child into what i assume is functional adulthood. You may think you are equipped to handle these issues due to your history of successful parenting. But with stepkids it's different. You aren't allowed to have as much of an influence and it sounds like BM may actively work against you. I would recommend waiting to cohabitate until the deal-breakers are in place and stable for minimum 3 months. I agree with ESMOD that having the adult bedroom be adults-only is a good first step. You can't have you, your SO, and 2 kids all in the bed, and you will want your privacy. 

Dont do it. Your bf is going to put you through hell and you will be blamed. Then next thing you know, you are stuck in a lease or in a mortgage and living somewhere you cant move out from with ppl who clearly dont want you around and would love to put you out

None of your plans or goals will work....You will end up tired and experience all kinds of losses. Save yourself....Perhaps keep the relationship between you when his kids arent around if you really really like him that much

Go on the offensive. Hire a PI, get proof that she is violating the morality clause in the CO.  Then... when she squawks, bare her ass.

You have major problems.  Don't move in until it's all straightened out.  This is a paper and pen making list discussion.  Most SM want there bed room off limits to SK.  Nothing wrong with that. Tooth brush now then makeup, clothing. Jewelry.  SK taking over the bed. No,  ..No... No.  

BF is the parent, he must be home to parent.. not working too much.  This is not ok in second SK  relationship.  There has to be rules.  Bed time... kids to bed as in there bed at x time each night.  No staying up in your adult time.

You are not. Repeat NOT  those kids mother. They have a mother and father, you are not one of them.  You can not be in a  life long fight with BM. This is no way to live. Saying so, SO must have limited contact with BM.  Mostly by text or MFW .  Not phone calks three times a day.  At 17yo, 10yo and 6 he should be in contact with kids not BM. 

'THINK .. Your SO is being unreasonably in his thinking.  He might be better off not in a relationship until he's ready for it,

Speaking from my experience, I don’t think it’s a good idea for you to move in with him yet. 

Red flag number 1: he has 50/50 custody with a narcissist BM. This is your first BF with kids. Do you know anyone personally who dated a man with a narcissistic BM? If not, read around on this site. No amount of your good intentions is going to be win out against her campaign against you via her kids. They are already reporting back to her what you are doing (the bedroom), which means on some level your presence bothers them. And this is only the beginning of things they are going to go back and forth about.  They won’t stop sharing what goes on in your household and will report any slight they perceive and you won’t like it. 

Red flag number 2: “they really don’t have a lot of structure between either home”.  This means that you coming in, with all of your rules, boundaries and expectations are likely going to be seen by his kids as the bad guy. Right now they’re allowed to go to sleep with the tv on, in his bed. They will interpret the changes you want as you replacing them and they won’t like it. They already act out, with no consequences and you coming in to their lives and setting rules I’m sure will not go over well with them. And they will act out against you. The girl hits, the boy has meltdowns, it sounds like a loooong road! 

Red flag number 3: “time is also an issue, he works 40 hours and runs a business”.  What time does that leave for him to parent? Help with homework, setting consequences for bad grades? Or are you expected to do that? The kids are already lagging in school AND behavior, and your boyfriend is a part of that parenting equation that results in that, even if it is because he works too much and doesn’t prioritize parenting. It’s nice that he cooks them meals, but like you, I got fooled into thinking “awwww, that’s so sweet! A man who cooks for his kids!” That was because in my life up until that point, I had never seen a man who regularly cooked for his kids, and my own father never did these things so there was that.  But when DH was still doing it when the kid was 17, it was annoying and the 17 year old barely ever cooked, much less even for himself. It was almost as if he refused to learn, because he knew DH on some level likes to feel needed and useful and doesn't mind cooking. 

What is the plan for launching the 17 year old? Or is he just going to flunk out of school and live with you guys? 

You’re already driving them to school? You’re setting then bar a little high for yourself, now if they are late, it’s on you. I wouldn’t take on too much for stepchildren, you’ll see what I mean later on. I get that you're just wanting to be helpful and bond, but I would take on less responsibility and only do “fun” stuff every now and again. They, and you will appreciate this approach more.

 On my journey, I learned that parenting is so much more than just cooking meals for your kids. I don’t have to tell you, you’ve successfully launched your daughter but I was childless when I met DH and I was ignorant to what parenting required. If I had to do it again? Hard to say because I don’t regret DD, I planned her, she wasn’t an oopsy baby. But….this blended family experience NEVER blossomed into what I thought it could be, and I stand by the fact that it was them having a mom who poisoned them. Just the slightest drop of that poison is enough to destroy the peace in your home.

When I got into this, I did think it was as simple as just communicating my boundaries and being respectful to his kids. Thought that would be enough to grow to a place where we all loved and trusted each other, but that never happened, because their mom had influence over them, and they in turn acted out in my home, sometimes against me. 

I will say that since I no longer live with his kids, I feel a lot better about going home. But that was 11 years of toxic shit, and feeling like eggshells in my own home. 

What are you getting out of this? what’s in it for you? Is he an awesome partner? This is important because it has to be worth it for you. When I met DH, I thought he was great but after living with him a couple of years, I was able to see the dysfunction better. The craziest thing was that the very month I had decided to get back on birth control and try to move out (but continue dating him), I never got my period to start my pills. The 6th month of trying we got pregnant, and there that went. I stayed mostly because I didn't want my daughter to grow up in a broken home, plus while I love DH very much, he is not a strong parent at all. The first 2 kids he has, who he had custody of, turned out to be selfish, screwed up people. Not evil, but definitely not the people I thought they could be. Part of that was also DH's fault. It was too late when I realized he was very head-in-the-sand about his kids, and I knew if we divorced, he would be that exact parent to our DD, and she would have been exposed to his kids without me around, so I stayed and sucked it up just to not have to split her between him and myself. I got lucky in that my DH does love me, and does try, but it took for me to pretty much kick his kid out last year and almost divorce him to get my peace back. 

You’re about to move into a home with a man who is super busy, has 50/50 custody of 3 kids who are not performing well in school, and don’t know how to emotionally regulate. The peace you currently have will be gone. I would at least sublet/rent out the current space you’re in, so that in case it goes to hell, you have a way to escape.
 

The fact that your SO sleeps with his children because he doesn't like to sleep alone is so wrong on so many levels I don't even know where to start. And his daughter is 10, the age at which many girls start to develop. Please read all of the warnings you have been given and get everything worked out with this guy before you even think about moving in with him. If you don't, there is nothing but heartache in your future.

No one could pay me enough to move in under these circumstances. 

I have to ask, when did you decide this was a great idea ?  Has anyone in your circle told you it is not real swift on your part?