plus, Obito might be some years older than Kakashi, considering Kakashi was promoted very early on. maybe two or three years difference. and he matured mentally while being crushed under a rock that turned on his self-target MengkyouTsukami (whatever illusion) and he lived through all the pain of being crushed for what seemed like years.

however, due to how crazy b1gdawg's suggestion is, I'm going to support it. Obito is Sasuke from the future\past.