I knew it. 'Ciel' will never kill his brother off just because of his jealousy, etc and to take his place. He did it to fulfil his wish. He didn't kill the real Ciel, I'm glad the author did not make him out to be e bad guy. It's unlikely for Sebastian to lie about the soul of the real Ciel too. So I'm guessing, the undertaker brought him back. Either he succeeded the experiment and now 'Ciel' has to kill his brother for real or the experiment failed and his brother crumbled to insanity like the other subjects.
AN ANGEL!! Hikaru is such an endearing child Lol everyone is shipping Matsu and Yuuki, even their new neighbor!