If you think about it, identical twins are pretty crazy - two people who look exactly alike. It goes further than that though, identical twins have the same DNA. So what does that mean if a pair of identical twins marries another pair of identical twins and then each couple has a kid? Well, things get even crazier, and that is clear on @ThePeterTwins' Instagram account.
The page is run by two men, both named Peter, who look exactly alike, except they aren't identical twins - in fact, they aren't even brothers - they're cousins. Their moms are identical twin sisters and their dads are identical twin brothers. Each couple had a child and both chose to name that child Peter. Because their parents' DNA is the same, both Peters' DNA is incredibly similar - so much so that on a DNA test they'll come up as brothers. They are what is known as quaternary twins.
The boys tried to break it down in a recent post.
One question they get asked often is if they have the same birthday, but remarkably, one Peter is four months younger than the other.