They say age is nothing but a number, but it’s so much more than that in Hollywood.

You probably wouldn’t suspect that some celebrities are actually younger (and sometimes older) than we thought them to be. Maybe there's some secret youth serum being passed around Hollywood that we don't know about (yet), but it's becoming harder and harder to tell just how old these stars really are these days.

Now, the age-guessing game has always been a fun one to play, and so we've put together one of our own. So would you believe us if we told you that Pretty Little Liars' Troian Bellisario, Mary-Kate and Ashley Olsen were all the same age? And how much would you freak if you found out that Jennifer Lawrence and Sarah Hyland share the same birth year IRL?

Click through our gallery above to see which celeb pairs are the same exact age.