Originally posted by: Gen
Im pretty sure his brother meant that sasuake would be the 3rd user ever. Its a "very rare trait" of what is a rare trait to begin with.
Pretty much.

But keep in mind if Kakashi could have acquired Mangekyou before the entire Uchiha massacre. Perhaps Kakashi was the first to ever use it.

I don't beleive this myself, it's just a possibility. I'm of teh opinion that the first user ever lived long before Itachi and wrote down all the secrets of the Sharingan in that room under the tatami mat.