Reading between the lines with X-Men Number 8, they may have resurrected Vulcan when he was not actually dead [just that everyone thought he was dead.]
Thus we have two Vulcans linked by dreams / thoughts, and the Vulcan on earth (now in space) may not have all the memories of Xavier's manipulations and the Shiar wars due to him being in space / recent resurrection when Xavier was depowered. Yet his other alive self does have those memories.
WOE, the Fire inside of me is Fire.
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Recheck out Sinister Secrets #7
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But yeah this indicates why there needs to be an X-Factor. I wonder what would happen with Young Cable vs Old Cable, or perhaps Young Cable and X-Man if X-Man ever returns (technically not the same people, just similar enough genetically that they have feedback with one another.)