Your BF is the problem here, not the kids. He lets his kids be disrespectful jerks to you.

Sorry to tell you it does NOT get any better with a passive daddeeee. Time only defines the problem more precisely. Most of us here deal with this syndrome -but with kids of all different ages.  From experience I can give you about a 100% garantee the kid adults are no better,  maybe worse and more aggressively manipulative to the SM, whom they do not want around.  They spend an inordinate amount of time working to destroy your marriage (or relationship), any way they can, if dadddeee cannot put a stop to it and most for a myriad of equally sick reasons-- do not. 

If you are seeing this now, it might be a great time (before you are married), to think about it you wish to deal with so much worse to come.  

The problem is daddeeee and daddeeee's inability to parent his kid is unlikely to change in the future.

I feel your pain! My SS13 lives with us every other week and I have been in his life for 4.5 years now. To this day, he has never said a word to me without me initiating. I am not even kidding! Even when he does answer, it's usually one word answers and little to no eye contact. His 3 older sisters never moved in with us and chose to stay with their mom. My husband only moved in 1.5 years ago after 3 years of dating so it wasn't even a quick move and we gave them time to get use to me. 

I am just polite around him and no longer make an effort to go out of my way for him. This is odd because I absolutely love kids especially my own. However, after years of trying I just simply gave up. I don't care anymore. Not my kid, not my problem! When my husband asked his kids why they felt uncomfortable around me, they said I was always inviting them to the movies or out to eat!! What a BITCH I am lmao! How dare I want to treat them to a nice meal and movie and spend money on them! 

Sadly I have all but given up and I don't give a crap about them. I try to not be generous with them or buy them anything. This is so not me but this is how relationships become after years of trying and being rejected repeatedly and ignored. On the surface, I am very kind to them but I would ever go out of my way for them! Disengage for your sanity!

My DH is afraid (deep down I think) that SS won't want to live with us anymore so he let's him do anything he wants including playing xbox for 16 hours a day in his room with the door shut. I shouldn't complain though because at least he is out of sight and mind! When his dad isn't here, he brings his food upstairs so he can continue to play xbox. I use to worry and say things to his dad about his sons behaviour but he didn't do anything for fear that his son would leave (my opinion but he wouldn't agree I'm sure). He doesn't have games at his mom's house so he likes being here only for the xbox and lack of parenting lol!

My kids however, live here full time and are happy, outgoing and well mannered (not just my opinion but teachers and other parents) so I just focus on parenting my kids and let SS do his own thing. I hope that maybe he will get some social skills passively just by living here :  )

Good plan! For your survival, just stop trying. Be polite to them and fake it but don't go out of your way. I used to notice his short pants and buy clothes for him (using DH money). Now I don't say a thing. I do wash them and make his lunch with the other kids but I only do these things if I am doing it anyways for my kids. I love my DH very much so I do this only because it is his son. 

Oddly enough, my kids adore my DH and my youngest daughter calls him daddy since he has been the strongest father figure in her life since she was 2 years. My 12 year old son also adores him and considers him to be a Dad even though he calls him by his first name. The older kids also love and respect him. Sometimes I am secretly jealous and he got off so easy in the step world when I am only treated with silence, rudeness and ignored despite the fact that I did nothing to them and only gave them love and spent money on them.

Step mom's have an unfair disadvantage. Step dad's are often treated better for some reason? I guess society has made stepmothers an evil entity to be hated and never trusted??

I hold strong to the knowledge that eventually he will move out. Start the count down!!

It's mind over matter! Just stop trying and caring for your own sanity and survival!

Life lesson for him - most people choose to ignore aholes rather than give them lots of positive attention.

You sound like an awesome woman trying to do the best you can to be a real family and make sure his kids always feel included. His kids sound like spoiled, self-centered, entitled jerks and if I were you I'd pull back and stop giving them so much attention. I dont think I'd disengage completely but I definitely would stop going out of my way for them, especially if it meant I was doing more for them than for my own kids.

I can relate. My boyfriend's oldest barely speaks to me and isolates himself from the rest of us. His youngest I feel like I have a chance to build a relationship with. However, I just had a daughter with my boyfriend and am a first time mom. I love my daughter and pretty much only want to give all my attention to her but I definitely do what I can to include his kids. I'm going to keep trying for now but if things don't improve then I will just completely focus on my own child. 

There's nothing else you can do and I don't blame you for not wanting them around. It sounds like they're dead set on not bonding with you and don't care to have a relationship with you. Just enjoy your own kids who need you and love you unconditionally and forget about his kids.

Girrrrlllll, OMG I feel you. I have 1 SS9 (who we have full custody of) and my DD9 and DD5, and DD9 and SS9 are ALWAYS fighting over something. MY DD9 cares way too much about others (yes, it's a good quality for future nurses or doctors) but my SS9 is SO effing mean and hateful I CANNOT stand him. He literally will walk in the room, say hello to his dad and completely act like I'm not there. God forbid I have to get onto him for something, then I am treated like I am the meanest person alive. My DD's are both amazing kids, they're honest, kind, get awesome grades in school, they fight over dumb crap but that's because they're sisters and have to share a room at the moment while 'wonderful' SS9 gets the bigger room for whatever reason. I just remind my DD's that when we get a new house (very soon), they each get their own rooms. 

Anywho, my SS9 is horrible. He only acts like a saint when my bf is around. I mean he really goes overboard, cleans in front of him, acts like he's the nicest kid to my kids, but bf walks out the door, its like Dr Jekyll/Mr Hyde. My DD9 sees right through it. We talk when we are alone on car rides home and she tells me pretty much what I think of him. SS9 plays his dad like a fiddle, I've told my bf that too. He doesn't see it but I've completely disengaged. I've told my DD9 to not even acknowledge his existence if he's going to be ugly. He's failing the 4th grade, but gets to play video games and watch youtube all night, because it's "not his fault he has adhd". Little do they know, DD9 is an unmedicated ADHD kid, and she does just fine. We even got a letter that he's going to fail if nothing changes, and nothing has been done so.. not my kid, not my problem!! You want to destin him for flipping burgers and/or in prison orange, so be it! I count down the days til he goes to his mothers for the weekend and honestly I wish she'd take him more and be more involved.