My theory about who tobi is and his relationship with madara..
please it may be long so please read all of it, u will understand, and thats why am not going to use manga pages for proof coz it will be very long, just remember as i state them,
So here i go,..the proof from manga i will say it last, 1st the story
Madara's brother died and madara left the village, he was ambitious as kabuto, wanting strength all the way, so he was always researching. Madara came in contact with Muu and his student Onoki, 3rd tsuchikage as you saw in the manga, they fought and Muu used his technique that splits him into two,..but madara's EMS was too good and he coped the technique.
Madara did everything as he read it at uchiha tablet,
Madara returned to the village where he fought the 1st hokage Hashirama, and he stole his DNA, but as he could not win, he split himself as Muu did, the first part finished the battle as his second part teleported from the battlefield with Hashirama's DNA,..and he lost but dint die,.but also Hashirama was injured so he could not take his body but returned to the village for help to get madara's body only to find that it was not there, when the second part madara had returned and took it, so the village left.
As you have guessed he part that took off was tobi and resurrected madara stayed and beaten terribly,..but they did not merge after that, they researched and then madara got the rinnigan using hashirama's DNA,. but madara's body was too weak to handle the Rinnigan, and since they had separated so was tobi's body, so they kept it.
Proof as the story goes on, Some years passed but they dint forget their plan, as witnessed in the manga, Kisame's back story, madara was the one who invited kisame into akatsuki, proves he was still alive even then. Yes madara and tobi wanted the rinnigan to develop so they found Nagato who had alot of chakra as an uzumaki very young and handed him the rinnigan.,
But unfortunately madara was going to die so he left a huge mission for tobi so he can revive him with rennitensei, and come back to life. But nagato was a kid with undeveloped rinnigan so he could not do it, so tobi followed nagato to his growth waiting for the moment the rinnigan develops so he could revive madara, but instead he used all the development madara was waiting for to revive the leaf village, thats why tobi said that nagato's power was supposed to be his, meaning to revive his other half. And thats why tobi said he was an empty shell of his old self. But as nagato stated that he could revive only those he had killed after he entered the village, and also could not revive Yahiko beacuase rinnitensei has its time limits so by the time he got that jtutsu yahiko had died a long time ago. So even if tobi wanted to revive madara he could not because it was a long time, so tobi decided to collect the tailed beasts to use their mass chakra to bypass the time limit and revive madara who had died long ago.
What do you think triggered tobi to start a war to get Naruto and Bee,. after Nagato's death tobi's hope was lost as well so he decided to go on with the moons eye plan as he is, with out reviving madara. But near the start of war thats why tobi was so suprised to see kabuto summon madara but it was no use because he knew they could no longer merge, so was not interested. And when madara was summoned by kabuto, he already knew that before his death the plan was for tobi to use nagato to revive him, but was disappointed to be revived as an Edo.He could also use the rinnigan due limitless chakra of an Edo.
So let me stop explaining for it not to be too long,
So Tobi is Madara, also another proof, is that Muu said that splitting jutsu also splits his powers in half, so Tobi went with the teleporting powers, That's why Madara does not teleport, yet even the 4th hokage said madara could teleport, because tobi is the one who can.
So any plot-holes in my theory yet to come?
