I'm thinking that there were two chains that are from the Uchiha clan, and this was during the time of masses and izuna. I believe that maybe the MS abilities are from specific lines of ancestry, like maybe Sasuke and Itachi are descendants of Madara seeing as they all have similar MS techs. Then I think Izunas MS techniques were space-time and maybe the genjustu kotoamatsuki and these abilities were later passed down to shisui and obito, meaning they're descendants of Izuna. This is why Tobi and Kakashi have similar techniques, because kakashis eye comes from obito (a descendant of Izuna) and this means to me that IZUNA=TOBi. I know this all seems far fetched but it makes sense in my mind. So if you need clarification let me know 
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