Personally, I wouldn't separate the cats. They are still pretty young, and the little one still needs the nurturing only another cat can provide right now. It would be pretty upsetting to the little one if he is that dependant on the older one at this time. Just give them time and it'll all work out. Don't force yourselves onto the little one or it'll take even longer for him to come to trust you. Just try petting him while he's eating, sleeping, and relaxed. It won't happen overnight, but it will work.