My baby, Harrison, was OOP December 17th, 2017. Whenever we go to the playroom, everyone runs around and has fun, but Harrison will chase the girls and once they stop running, he will grab on their back with his two hands and won't let go. Sometimes, it even seems like he's nibbling their skin, but most of the time it's just his hands. The girls will try to run, but since he's the same size as them, they can't, so they'll turn around and nip at him to get off. He doesn't until we intervene. I'm wondering if this is just because he is still so young and lived with his parents for a while, so maybe he's used to clinging to Mom's back? Would he be thinking Pepper (my glider he usually does it to) is his mom/mother figure? If not, what else could it be? I don't think it's harming anyone, they don't do it in their cage, just in the playroom.

Is he neutered?
It could be that he seeks to cling on older gliders in play room because he is lost in a big room (plays the baby)
It could also be asserting dominance, especially if he is not neutered, and if one of the female is in heat...

He is neutered, yes.