We are not married yet, but planning to soon. He is a little older than me. My family lives on the other side of the planet and there are cultural differences that are present (it is a strengths in my opinion, but can certainly present difficulties as well sometimes). Almost all of his family is here or relatively close, he has a career, a job, a house, and a 17 year old daughter who he raised alone (divorced his wife, fought for custody and eventually got should custody of her). He did not re-marry after until he met me.
Now, I feel like a horrible person, but I am having a hard time emotionally with the daughter. As I mentioned, she is 17, but developmentally she is behind. And only with certain things. I will try to explain in order and to an extent that I know about what has been going on. They divorced when she was almost 2 years old. Even then she was already behind her peers. The older she got, the more it was obvious that she was behind. Her daycare did not want to accept her because they did not know how to deal with her. She was unresponsive, did not talk or play with other children, disengaged and I don't even know what else. He had to fight with that daycare to get her additional support and to keep her there. He had to fight with schools, doctors, etc. all the time. They supposedly had the best pediatrician in town, but that pediatrician somehow failed to recognize that she couldn't hear well. She had 4 surgeries in her ears at the age of 6 or 7 (I forgot) and she finally begun to hear. She was in speech therapy for 10 years. She was in special ed for most of her school years except the last year when she is a regular classes. She is not a brilliant student but she does okay. There were doctors consultations and board meetings and she was never diagnosed with anything that is commonly known (ADHD, Autism etc.) but anyone who ever meets her and spends some time, would notice that something is "off", but what is "off" is unclear,
She doesn't have friends. She doesn't strike any conversations. All of her answers are one-word answers. She constantly plays video games. She is not interested in doing anything active, going anywhere (it is rare that she will actually want to go do something), she doesn't like learning things like cooking, cleaning etc. She was not made to do any of those things for the longest time, so now the extent of what she will do is microwave food. She did learn to put her laundry in the washing machine and press the button...she can sleep. She showers. All of these things took a lot of effort on her father's part, because although she is capable (and I now believe that she is), those are the things she prefers not to do. She needs EXTREMELY detailed instructions of how to do something because she lacks an insight or common sense and won't figure things out on her own or learn by observation (or will just pretend like she has no clue how to do something - that happens too, which annoys the crap out of her father and me to be honest).

Well, so the thing is that she lives with us. Or, rather, I live with them now. The mother is out of the picture. It is extremely unlikely that she will be out of the house any time soon. In fact, I feel like she might be with us for a very VERY long time and I try not to think about it much, because then I question why did did this to myself (signed up for a step-mother role). I love my soon to be husband. he is a great guy. I think he will be an awesome father to our child (I am expecting, he is thrilled, she wants happy about it and said "I am not ready"), but I don't like her. It is not even that I don't like her per se, because she has never done anything BAD to anyone. But I find it extremely difficult having this 17 year old in the house, who never really talks much, sits on the couch all day playing video games, has very poor social skills, doesn't show emotions, doesn't have friends or do anything that a 17 year old would typically want to do etc. etc. And I fear that it will never change and there will always be this presence of someone like a "roommate" who is very odd and it makes me feel very uncomfortable.
She likes me in her own way. She tries to show it in her own way (like come up to me, hug me like a 5 year old and say "I love you"), but I always feel weird responding to those attempts, because for one, I actually don't love her. I never will LOVE her. She is not my child. I respect her, I will never be mean to her, she is my husband's child and is important to him, but that is where it ends for me. I have a hard time connecting to someone who can't connect with others.
I can't talk to him about any of it because he is extremely sensitive when it comes to her and is very protective. And my family is far...So I often find myself at home with her alone (my husband works very long hours and mostly nights, so he sleeps during the day and is gone at night) and it is hard for me. We are not even married yet, but I am already thinking about how it will probably get worse when i get a real feel of the entire situation....It is one thing to be a parent: you are bound to love your child no matter what and how they are, but I don't have that attachment to her and she is not really a child any more...

I don't even know what kind of help I am seeking here. I guess I just want to somehow feel happy despite the circumstances...