Yeah like what was said before. This is defiantly something that appears to be happening on purpose. You need to sit down and talk to him and tell him how you feel about it and give him some of your examples as evidence. if he really does love you and wants to be with you then he shouldn't allow his parents or sisters to treat you this way. its not fair on you when you seem like a very pleasant person. don't blame yourself as its not you its them. he needs to stick up for you and show them that you are part of his life and you will be part of theirs. if he says you are bitching about his family then he isn't worth it just let him be that way. He has to know how you feel and that it is not fair. if he don't believe it then ask him what else it could be and give him the metaphorical example of your family doing it to him. its not your fault just talk to him and if that don't work ask them what's going on.