is there a reason i see my boys lick each others butts? i think they are or smelling or doing something back there

Are they only doing this after they have been away from each or after you've handling them? They could be making sure they are the same as when they were parted. Mine always lick and smell each other after my alone time with each one, not sure if they are just cleaning each other or if the smell my scent on them and need to check it out.

As long as they are not hurting each other, I don't try to stop them