I've always thought that Charles power was like Peter's power (or like Peter's power used to be). I remember there were some things he said in Season One that led me to believe that:
When Peter traveled back in time to Charles rooftop he said something like "Invisibility, I always wanted to try that one."
Anyway, I remember a lot of speculation about that way back when I first signed on to this site, and that was just the consensus I formed.
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i totaly agree i do remember him telling peter that. that would make the ,most sense