[Prediction/Theory] Sasuke and Itachi are direct descendants of Madara Uchiha
As most of you probably noted, Itachi, Madara and Sasuke are the only ones that have the Mangekyou who can use Amaterasu, Tsukuyomi and Susanoo.
The other people that possessed the MS, namely Kakashi, Obito and Shisui all had different abilities. I think it was Itachi ( needing source ) that said the MS gives specific abilities to each wielder, rather than every MS user having the same jutsus.
It is not fishy that Sasuke and Itachi would have the same MS jutsus. They are brothers by blood. But why does Madara have the same jutsus? It certainly feels fishy to me. You will note a load of similarities between Madara and Sasuke.
To further strengthen my theory, Naruto has been described as possessing the Will of Fire ( Which originates from Hashirama Senju, Madara's eternal rival ), Sasuke has been described as being afflicted by the Curse of Hatred.
All of the konoha people have their issues. Neji's father was killed because of Konoha's order ( his twin was supposed to die and Neji's dad took his place ) yet only Sasuke defected and wants to destroy it.
The curse was almost extinguished by the creation of Konoha, with only Madara Uchiha refusing to relinquish it.
I believe this is similar to how the Konoha 11 / all of Konoha except for Naruto decided to kill Sasuke given the chance.
Though Madara was exiled by his clan soon after
The Kyuubi noted Sasuke's chakra was alike Madara's ( possibly due to his Hatred, or it might be another hint that they are related ).
During the Battle between Naruto and Sasuke in Part I at the Valley of the End, Sasuke stood atop Madara's statue, with Naruto being on Hashirama's.
Both Sasuke and Madara obtained their EMS from a loving brother that sacrificed themselves ( Izuna because he thought Madara had to lead the clan at all costs, going blind and even continuing to fight in wars blind while Itachi protected Sasuke all of his life ).
Both Madara and Sasuke hated and greatly admired their rival ( Hashirama and Naruto, respectively ).
Sasuke is the last Uchiha alive ( with Tobi being half-Zetsu ), probably being the only one that can revive the clan.
There might be others, but that's all I can think of.
- Same MS jutsus.
- Wielders of EMS gained without violence, with their brothers selflessly sacrificing themselves.
- Assuming Sasuke manages to revive the clan, both will be remembered as leading figures of their clan.
- Possibly most passionate wielders of the Curse of Hatred
- Both are rivalled by a strong wielder of the Will of Fire
- Both tried to destroy Konoha, feeling betrayed ( Madara by his clan, Sasuke by his village )