I think the Kennedy and Lincoln "after" pictures need a little doctoring.

#26 - incorrect. At the end of his term, Kennedy's head was in pieces and his brains were all over his wife's dress and the car he was riding in.

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What if the presidents are actually in on some big secret that causes their aging like conspiracies with aliens or maybe they are time travelers that are actually aging at a normal rate but spend a large portion of their life traveling outside of normal time? Nah forget I said anything.