Well, your second paragraph says it all -"she was raised by my husband's exes and nannies". Why didn't your H raise his own kid? She's likely been damaged by losing both of her parents. Does she have a therapist?   I imagine she doesn't think you will stick around any longer that the other multiple people who have "raised" her. 

Hello, I'm not sure how to start this and it's my first time ever trying this. My girlfriend and her 14 and 5 year old sons and I live together now. Issues with the kids are starting to really affect our relationship and I want to figure out how to fix that. The 14 year old is ALWAYS a problem and has no remorse or regret for the problems he causes inside or outside of the house and my GF has had him in this program with crisis support for the past 10 years now ( which I think is a joke cus they haven't changed anything in ten years). I've actually learned to almost tune him out for the most part except when he's really disrespectful towards his mom or aggressive. It's to the point where my GF starts getting severe anxiety moments before he's about to get home wondering what kind of crap he's going to start today, which hurts me to see her like that. But ontop of that is something I don't think she sees is a big issue causing many problems with us, her 5 year old son who is attached to her hip 24/7. If I want to spend time together just her and I, I have to wait until he's asleep. Which is a problem by itself since he's constantly up til midnight and by the time he's asleep now one of us are too tired. He still has a sippy cup that he demands for milk saying "mom cup!" He will wake up from a dead sleep and his first words "mom cup" no bs. He will only drink milk and won't eat anything but peanut butter sandwiches, pancakes, pizza rolls, and other junk food which his mom thinks is perfectly ok. We literally can't have a family dinner because we'd have to make something for her and I, something for the 5 year old, and something for the 14 year old. I say we need to make a meal and if they don't eat what we made they don't get anything else, that's always worked in the past because they will eat when hungry. It's not like I'm saying they can't eat anything, they wouldn't be starved we have plenty of food. I don't think she sees the damages being done by constantly catering to there every demand, especially the 5 year old. If I say anything she immediately deflects it to me or says that I wouldn't understand cus I'm not a parent, even though I've helped raise many kids, and that I'm being mean to them by saying anything when they do something they shouldn't be doing in the first place. Why am I always labeled the bad guy when I say something about it? These kids NEVER get any real consequences for anything and no kind of real punishment, even just standing in the corner for 5mins, there's no follow through at all so they don't fear doing anything wrong.