Go incest!
OF COURSE THEY WILL END UP TOGETHER!
Though with our luck it'll probably be one of those "I love you!" "I love you too!" *one of them dies* moments. *Sigh*
I hope they admit their love and stay together forever. But I doubt that will happen.
I think they really are siblings but will of course, be pleasantly surprised if they turn out not to be. But like I said, I don't care either way.