Why do some people look so weirdly older/younger?

In My Humble Opinion
41

Back when my grandaughter was small, she was buying something in a store with her own money and I was standing fairly close by. The cashier (probably 19 or 20ish) briefly looks in my direction and says to my grandaughter “did you ask you dad if that was ok”? I said to the young lady “that’s grandfather actually” She said “I’m sorry” to which I advised her “that is a mistake you NEVER have to apologize for”. She had kind of a stunned look on her face as I don’t think she understood she had given me an accidental compliment.

Like getting carded when you ask for the senior’s discount.

42

I think it’s mostly the picture itself; if you google “Mark and Steve Waugh”, you get a bunch of photos of them, and in most they look pretty much the same age- in particular, the one on the left in the OP’s photo doesn’t look quite so young in most of them.