its awful for you, dd and your boyfriend
your boyfriend probably believed his family as when they gang up they can be very persuasive
his family knew damn well that they would make him bring her over once they got him over the first hurdle which was to get him married, they have been taking it one step at a time with him, eventually he will give in
i know i am going to get lynched for this, but i cant help feel sorry for your dp too, because he is stuck in the middle...he loves you, he loves his family, wants to make you happy, wants to make his family happy
he is a big boy and should stick up for himself and put his foot down, but for him there is a lot to lose, and as long as he knows your going to stick around, its easier for him to keep his parents happy than it is to keep you happy
hope that makes sense, im on your side, i just want to help you see it from his side