CAUTION: It's a long read ahead but to anyone who is in a relationship where adult children exist...I'm begging for your advice.

Let me start with a bit of an intro because I'm not sure if my previous posts are still active. I originally joined this board like 8-9 years ago when I was in a previous relationship. He was 10 years older than me with 4 kids, and they were all under the age of 18 when we first got together. I broke up with him a little over 4 years ago, and it was the best decision I've ever made.

I've been with my current boyfriend for about 3.5 years. We moved in together about 3 years ago, which for both of us was more for financial reasons than relationship reasons. I was renting and the lease wouldn't be renewed because my landlord was selling the house. My bf owns his house and had been considering a roommate just for extra income, he didn't necessarily need it but figured it's a big house so why not take advantage. However he didn't like the idea of a roommate, because he's very much the type who likes loud music and walking around naked. So when I said something about my lease not being renewed, he asked if I would want to move in with him. We discussed the pros and cons given we hadn't even been together more than a few months when this came up, but agreed that if things didn't work out, I would stay in a spare bedroom until I figured something else out. Basically we made a "worse case scenario" plan, but fortunately it worked out for the best.

He is quite a bit older than me (I'm 35, he's 53), but it really has never been an issue. It initially deterred me from seeking a relationship with him at the start, but we both realized that it worked really well and just went for it. Thankfully, there hasn't been anyone who has vocally been unsupportive of us. We are very happy together, and he has even told me on multiple occasions that this is the happiest he's ever been in a relationship, including when he was with his ex-wife. They started dating in high school, then divorced around 2013 I think. So they were together a long time. He does have 2 adult kids (23m & 25f). I have always gotten along with them, although I've never gotten the "warm fuzzies" from either of them. I assume they have an issue with our age difference since I'm closer to their age than his, but nothing has ever been brought up that I'm aware of. I do my best be to hospitable and kind to them when they're here, I join in on conversations and essentially try to exist without giving them a reason to get upset with me. I personally never had any issues with either one of them and just wanted to make sure we could all get along so as not to cause a problem in our relationship. I have a step-mother, she wasn't the best growing up, and I really just did not want to have that same relationship with my (hopefully) future step-children.

Now let's fast-forward to the issue. Last November, BF had been working on his daughter's (24f) car and finally had it fixed, so he told her to stop by on a weeknight to swap out cars (she had been driving his while he had been fixing hers). She came by in the evening and I mentioned that I was making dinner, so she was welcome to stay and have dinner. We all ate, then it got pretty late and she made a comment about just staying the night. We have 2 spare bedrooms - one we call "my room" simply because it has most of my belongings in it and I use the closet, and then another spare room that usually has a bed in it but at this time was being used as a temporary foster space for kittens that a stray had (completely different story I won't get into too much, just need to give background). I told her she could stay in my room since the cats were in the one she would normally stay in, and I just got my work clothes out and things I needed for the morning so I didn't have to disturb her. I went to work the next day and came home to find her still there. I asked my bf, he said he wasn't sure when she was leaving but it wasn't a big deal because he didn't get to see her alot. Another backstory I should add is that up to this point, BF had been working out of town during the week for almost 2 full years. He'd leave Sunday night and come home Friday night. At this point, he had been done with that job for about a month and a half and was now laid off, so it was great to finally have time together because so much of our relationship had been spent apart. So, in my mind the last thing I wanted was his daughter staying there long, but obviously didn't say that because I know he doesn't see them much and I can't be selfish.

So this process of me going to work and her still being at home when I got back had repeated for about 2 weeks. I was starting to get frustrated, mainly because this wasn't planned, so it was a bit inconvenient given she was staying in the room with all of my stuff, and he hadn't bothered to ask her anyhting about why she was still there or how long she was planning to stay. She had her own place with roommates, so it didn't make sense why she was still here. She wasn't even spending much time with him. She'd spend the daytime in the bedroom, and then come out at night to eat dinner and watch TV with us. So basically the time I had with him was the only time she decided to show her face. Whether or not that was intentional, I don't know. Again, not that I'm incapable of "sharing," it just doesn't make sense why she would spend her days holed up in a room that isn't hers and not spend any of it with him since he was home. Then Thanksgiving came, she went to her moms house and was gone about a month. She left some stuff at our house, so I knew she was coming back. By this point, I think the only thing BF had figured out was that she was "fighting" with her roommates. She came back from her moms house, and first thing she did was go to her dad crying and ask him if she could live with us. He said yes, without hesitation. I understand as a dad why he'd do that, but I was also frustrated that there was no conversation with me. No, we're not married, but I do live here too and her living here was impacting me more than him. We didn't even have a room for her at the time, so this meant she'd be continuing to stay in mine until I could get rid of the kittens. He also didn't bother to talk to her about a plan. Like how long will you need to stay, what's your plan from here, etc. She wasn't working and hadn't been working for at least a few months, so I knew this wasn't going to be as short-term as he tried to say it would be.

This is getting really long so I'm going to try and shorten as much as I can while still giving the right information, so I apologize if it's all over the place. SD has stayed with her mom in the past, and I guess her mom told her she couldn't stay there again. SS is still living with their mom, but I guess he pays rent and is waiting for his GF to get done with school so they can get a place together. What I understood is that their mom "couldn't" live with her again, meaning it didn't go well before. Red flag, IMO. If mom can't live with her, how can he expect that it will go well here?

One thing to note about him is that he's very laid back and non-confrontational, and I can tell that his ex-wife was basically the parent when they were married. Meaning she had to do the disciplining, etc. because he didn't do well with any of that. Also, I did get the kittens moved out after a couple months and she is now moved into the other room.

Once she was living with us, it turned into her always being around, even on the weekends when him & I would go do things. We go out every Friday night, and he'd invite her along so she wasn't sitting at home. I tried to have him limit it, explaining that this isn't the same as when his kids would come visit and we'd take them out to eat. He brought her with for everything and paid for all of her food & drinks. It's not my money, but in my eyes at this point, he's being taken advantage of and it's pissing me off. She eats our food, runs up our bills, takes things without asking, and never pays for a damn thing. It would be different if she were working and trying to get herself in a better position, but she wasn't. That's what upset me the most. I had also witnessed her take his money off of the bar when he wasn't looking, and finally told him after the 2nd time she did it. It wasn't alot, like maybe $10-15 each time, and he'd always act like it wasn't a big deal. 

in February, BF got called back to his out of town job. After a few weeks, I made a comment to him how she never comes out of her room when he's gone. I rarely saw her, and she never came downstairs to the living room to hang out. I was 100% fine with it, but just told him as an FYI. He made a comment to me about how he assumes it's my fault and that I must make her feel unwelcomed. I was really upset by that comment, and told him I hadn't even given her the opportunity to feel unwelcome because she never comes around. It was her choice to stay away, and I wasn't offended by it at all but don't blame me for simply existing.

Then the big incident happened. Long story short, she stole something from the bar owner (who we are friends with) when we were out one Friday night and then pretended it was an accident and gave it back once she realized there were cameras pointing right at her. The whole thing was caught on tape, but even with video proof, she still claimed it was an accident. The only person to believe her was of course her dad. Her own mom knew it was a lie, but BF believes her because shes "a good kid" and "too smart to steal." Shortly after this incident, one of the bartenders told me that a couple months before that, a customer told her they witnessed SD take a tip off a table. The bartender never said anything about it before, but after all this she decided to bring it up just so we were aware. I never told my BF because I don't think he'd believe it, since clearly he doesn't even believe video proof. At that point, I pretty much lost any respect for her that I had. I was angry at the situation, angry at how he handled it, and didn't trust her being in my house. She claims it was an accident, but couldn't even bring herself to come back to that bar with us again because she knows he's the only one who believes her. My attitude toward her did change, but just in that I didn't really speak to her unless she talked to me first. I wanted to be respectful of my BF but just could not brush it off. I did explain this to him, and that I would never believe her and would have to figure out how to move forward and not be angry with her, but it wouldn't be easy.

There a couple extra things to note in this situation that I don't know where they best fit in so I'm just going to throw them in here. She did finally get a job a few months ago working like 12-15 hours for BF's brother overnight. She has private studen loans for schooling she never finished that BF cosigned on, which she isn't paying and caused his credit score to tank by like 140 points. She didn't officially move out of her other place until her lease was up at the end of March (she still had all of her belongings there) and had to pay rent for that entire time she wasn't even living there. I believe BF paid one month, her mom paid one month, and then she sold some stuff to pay for the other months. When she moved her stuff out, I was supposed to go with and help but she told her dad she didn't want me there. Originally he told her too bad because he wanted the extra help, then he decided to ask me to stay home. Which pissed me off because #1 she doesn't get to dictate what I do, and #2 he waited until we were just about to leave to tell me. But whatever. I didn't want to help her move in the first place but offered to be nice, so it worked out for me. I was just upset at how he handled it.

She also has depression and anxiety, which BF doesn't understand so he just goes with whatever she says. She supposedly was in therapy and taking medication, but still appears to struggle with it. After the stealing incident, she'd spend the entire week in her room, wouldn't even come out to shower. She'd be sleeping anytime he'd come home and try talking to her, so it turned into her just being here but we rarely saw her. I've mentioned in the most gentle way possible that perhaps BF and the mom need to discuss alternative options for her, like inpatient treatment. Because at this point either she was using it all as an excuse, or she needed more help than she was going to get being locked in her room all week long. Personally, I think she's using it as more of an excuse. Depression & anxiety are real, I suffer from depression myself, but it's not an excuse to quit living your life. You get help and work through it. So regardless of whether or not she's playing it up, something needed to be done. The frustrating thing is he will agree with me on things I say, but do nothing about it. So it was never a conversation that him and his ex wife had as far as I know.

At this point, her & I haven't fought about anything but he knows there's issues. I've expressed my problems & concerns to him, and idk what she's said to him about me. Most of my issues are in that I would ask her to do something simple and she'd ignore me. I asked her to stop keeping dishes in her room (she's literally right down the hall from the kitchen and would pile things up in there for WEEKS) and to just please rinse her dishes before she puts them in the dishwasher. I actually asked her that twice and the first time she just explained to me how she thought that was stupid. I didn't say anything at the time, but honestly I don't care what her opinion is. She's in our house, and she needs to respect the way we do things. Iasked BF to ask her to take care of cleaning the upstairs bathroom since she uses it the most, but I guess she had a "mental breakdown" over it but he couldn't explain why. I also told him after she moved all of her stuff in that I wanted the TV & Amazon Fire Stick back that I had left in that room for her. I had other plans for it and only left it in there for her to be nice because she didn't have anything. She had 2 TVs of her own, so I waited until she moved her stuff in and asked for it back. Apparently that really pissed her off, but BF couldn't give me a reason why. I would've never let her use it in the first place had I known she'd act like that. I wasn't being mean, she no longer needed it and quite frankly I have zero trust for her and wanted to make sure she didn't end up taking it with her when she leaves.

Her 25th birthday was at the beginning of April. BF told me there were plans for like a family dinner/party at a restaurant that was about 45 minutes from our house. He was still working out of town, so he was going to leave the out of town job and drive straight there. He said I could just meet him there, or if I didn't want to go, that was fine too. I said of course I'll go, I'll just plan to meet him there at whatever time he'll be there. The morning of the dinner, I get a text from him saying that he's been thinking and it's probably best I don't go until her & I can work out our differences. I immediately got pissed and asked him if that was true or if she didn't want me there. He admitted that she didn't want me there. I explained to him that once again, he's letting her dictate what I do. I have done absolutely nothing wrong to her, she's pissed for her own made up reasons and IMO, simply trying to cause a wedge between us and get me to leave. He told me that he wasn't happy with her for putting him in this position and that he'd talk to her about it later, but that I should just go along with it because it's her bday and he didn't want to ruin it. She was also leaving the next day to fly out to Boston and visit her best friend (her bday gift from her parents), so he wanted to wait until after all of that to address it. There was more to the conversation, but that's the brief version. The party was supposed to start at 5:45, and he got there around 6:00. I told him she hadn't even left our house until about 6:15, so she wasn't going to be there until at least after 7:00. He was the only one there because everyone else was at her mom's house waiting for her to show up. At 7:30, they still weren't there so he ended up coming home and never even got to see her or spend time with her for her bday. That pissed me off even more, she caused all these problems and couldn't even show up on time.

When he got home, I was in tears. I was so upset and frustrated at the situation. I have never said anything to her or been mean to her, any issues I've had I've only brought up to him. I even showed him our text messages, which clearly showed how many times I texted her to ask her something simple and she completely ignored me. I said it's on her how she reads any of these messages, I don't send them to be bitchy but I guarantee she reads them that way because she doesn't like me. She's making things worse than they are. I explained how hurt I was by what he did, and he felt horrible but I also understand she put him in a no-win situation. I said this needs to end, and when she comes back the 3 of us can sit down so she can air out her supposed problems and we can work through it. I also said I think part of her issue is she has no respect for me because he's never acted like my opinion matters. He never talked to me before agreeing to let her stay, and excludes me from every conversation he attempted to have with her about how long she'd be staying. (He tried talking to her about it a couple times but everytime she'd break down in tears, knowing he'd freeze and that would end the conversation. They had an agreement at one point that she'd get a FT job within a month, but she didn't and he never brought it up to her again.) I told him that there needs to be a plan, she can't continue to stay here with no end in sight, doing absolutely nothing for herself while living off of us and causing problems. He agreed that the 3 of us would talk about it and work out a plan/timeline for how much longer she can stay and when she needs to be out by. He understands why my opinion matters, and also realizes that he's incapable of having the conversation because she knows his weakness and can end the conversation by crying. He said the problem is that he told her that he'd never kick her out, and feels like he has no choice but to let her stay because her mom won't let her stay there. I said just because mom won't take her in doesn't mean you have to. You need to take back what you said, tell her you said that assuming she was going to be doing something for herself and working on getting out of this situation but that clearly isn't the case. We need to give her a deadline and stick to it. She's not going to end up on the streets, she will find somewhere else to go. She can act like the 25 year old she is and save up to get her own place. Or if needed, she has friends, other family, etc. she can stay with. She is causing problems here and if she's not going to grow up and take care of herself, then she needs to move on. Him & I have fought more since she moved in than we ever did in our entire relationship prior to that. We had the basics of the plan in place, but then she threw a wrench in the plan by not coming back after her trip. She's been at her mom's again for almost 2 months, but her mom wants to send her back to our house. Supposedly that's going to happen this weekend, although I don't know when.

I'm not sure if he's still on the same page given the time that's passed, but I'm hoping to get some outside opinions before I jump back into the conversation with him. Am I right in my thinking that I should be a part of this conversation? It affects me, I live here too, and quite frankly I don't think she'll try to pull as much with me involved. I just don't know if he'll feel the same way. I am worried that her being here is going to end our relationship. I honestly don't know what he'd say if she told him straight up that she wanted me out. I would like to think he'd say too bad, but he also doesn't know how to handle the situation and is trying to be a "good dad." He thinks he's been a bad one, simply because they got a divorce. His kids have never felt that way, so it's all his own thinking. I know that she's his kid, but I am his girlfriend and our plan is forever. I'm not just some girl he's been dating a few months. I get that kids are a priority in a sense, but at the end of the day, and especially when they're adults, you cannot put them above your relationship. They eventually grow up and move on to live their own lives. He cannot let her dictate his relationship or he will spend forever alone. Both of us have never been happier, and I am honestly not a bad person and have never done or said anything to her to make her act like this. His friend has tried explaining this to him as well, he's remarried with adult kids and said that his kids know his wife comes first. He will do anything for them, but they have to respect her and understand he will not "choose" them over her when she hasn't done anything to deserve it. I'm just not sure my BF can see it that way.

I apologize for how long this is. There's a lot of information to give and honestly this isn't even all of it. But it covers the bases that I think are needed for feedback. If you need clarification on something, please ask as I know I skipped around a bit and I'm sure I missed something. But any advice would be GREATLY appreciated!