Tobi is not obito..why Im sure of it?because if his obito he would be about the same age and body physique like kakashi when his fighting yondaime hokage
Well...I had joked about Tobi being Rokudo Sage's eldest son earlier in this thread, but with Tobi claiming to have given Nagato the Rinnegan, I'm not so sure it's a joke anymore. What if the elder son stole the Rinnegan from his father on his death bed, and had kept them in secret? Then, Tobi had disguised as a stone ninja and implanted the Rinnegan in Nagato, so nobody would guess what truly happened. And now perhaps through a jutsu of his own, or using Zetsu's power to mold a body, is using Madara's name and Obito's body as a cloak. I mean, it would explain why he knows everything about Rokudo Sage, and I gave a few images of support a while back, if anyone cares enough to look.
nagato already had the rinnegan before that. read it again when his parents were killed.
At that time he could just have a body of other uchicha and that's all (if he had, then it probably was Shisui's). After the massacre he just needed a body of uchicha that wasn't in the village or was known as dead.
I can see it now:
Tobi: You fools, believing I was Madara till the very end. I didn't even need to use my sharingan to pull off this illusion.
Kakashi: I knew it! REVEAL YOURSELF OBITO!!!
Tobi: wuhhh??? Who the fuck is he??? No, what you all failed to realise is that-
Narubo: But of course! Only one person could be as evil and twisted as you! REVEAL YOURSELF DANZO!
Tobi: wtf no! How can you all be so stupid? I even foreshadowed this as far back as Chapter 1... No there is only one person evil enough to be me... And that is...
Sai: The Jyubi?
Tobi: NO!!!! BOW BEFORE ME FOR YOU FACE THE MIGHTY WICKET BASKET AS FIRST SEEN IN PANEL 4 OF PAGE 39 OF CHAPTER 1 OF THIS ALMIGHTY MANGA!!!!!!!1111
*cue Kishimoto pleasuring himself while muttering "I've done it again"
tobi is shisui.