Juubi and Rikudou's brother? From the current chapters of Naruto, it is revealed, that Rikudou Sennin has a brother who also sealed the juubi in himself. That means there are two juubis in the world. If Madara has/had control of one of them, where could the other be hidden? His presence in the world for now is speculation. But as the Rabbit Goddess had Byakugan, this could mean that this brother may have been the Hyuuga's ancestor, which would mean Senju, Uchiha, and Hyuuga are indeed related, but Hyuuga and Uchiha could never be able to use the other's doujutsu, because of difference in ancestor.

So in essence, I'm asking, where could the second Juubi presumably be, is it not possible that the brother is the Hyuuga ancestor? For now this is all speculation, but I have a feeling that Kishimoto will end this series with a few plot holes, so I want to see other users' ideas on these questions.
I don't think there are two Juubis, because in the final clash between Ten-Tails and Kaguya's sons, Hagoromo and Hamura, they managed to defeat the beast and sealed it within Hagoromo. However, knowing that his death would unleash the Ten-Tails back into the world where it would continue its rampage and reclaim the chakra that humanity now possesses, Hagoromo separated the monster's chakra from its body and used his Creation of All Things ability to create the nine ,tailed beasts. Hagoromo then used Chibaku Tensei to seal the Ten-Tails' husk, i.e the moon.