Fighting?

My two baby boys have been bonded for like 6 months and are doing great! They cuddle and live well together!!

My only concern is that once they go out for play time, they will chase each other and try to mount the other. They are both boys, I know this because I do fur ring checks. They dont seem to be doing it aggressively. They popcorn and chirp and they dont do it everytime they see each other. There hasn't been any issues with them barking at each other or drawing blood. I know its probably normal behavior I just want to be sure that the mounting and chasing is playing or if it is something I should be concerned with. Better safe then sorry!

Thank you in advance!!