The possibly connections of Kagami Uchiha.
Okay, so Firstly I have to state a theory I have that involves the Sharingan. I remember reading somewhere that after a while, the sharingan began to appear less in the clan. I think how legends said you had to kill your best friend to get mangekyou were not exactly correct or when the Uchiha clan became diluted didn't didn't exactly fit the situation. I think there is an even more distinct bloodline in the Uchiha clan. I believe Madara is the start of the line that produced all known mangekyou eyes at this point in the manga.
Madara's children= Kagami uchiha. Izuna's Children= Fugaku Uchiha's father.
Kagami's children= Shisui and obito Fugaku's father= Fugaku Uchiha.
Fugaku's children= Itachi and Sasuke.
You look at this possible family line, and you can see that The mangekyou has appeared in the three known set of brothers, and has skipped a generation.
Kagami I believe is Tobi. Reason why? He was ashamed the Uchia had fallen so far. His father had been defeated by the 1st, The rest of his clan had gone soft and he was a natural enemy of the senju.
I think madara taught kagami alot of jutsu/ legend of Uchiha. I think he took DNA from the 2nd Hokage so he could utilise the space-time ninjutsu. I think he knew he would have a very powerful sharingan, but no mangekyou. Thinking ahead, he made sure e had two children, knowing they would be descendent s of the great Madara and when they had both got the Mangekyou, he would make one take the others eyes to get EMS and then take it for himself. Obito dying so young put this plan out of action, and i think it also suggests Shisuis reasons fro committed suicide so he would not be involved in that much evil ( he in-trusted Itachi with a mission to stop 'tobi' from getting EMS ever). There was still the posibility he could have taken kakashi's eye and formed it with danzo's sharingan he took from Shisui, but it was crushed( why he was soooo mad). I think he then followed Izuna's direct family line and discovered the first set of brothers was Itachi and sasuke, I think everything 'tobi' has told Sasuke at this point is a lie and he plans on taking Sasuke's EMS.
The Moons-eye Plan i believe was not just Madara's plan, but the whole Uchiha clans initial plan to rule the world, and Kagami is only trying to achieve it. however i think he has a much more sinister plan, and is more evil then his father.
Obivously there are a few loopholes involving Nagato and other Uciha related content, but I've thought about this for ages and honestly makes alot of sense.