I've noticed a few days while I have my two gliders out for pouch cuddles the boy's face and sometimes arms are wet. We have a boy and a girl, twins,they are about 7 months old and he is neutered. His eyes look normal and he dries off and acts normal at night. Has anyone ever seen this with Their gliders? Could the girl be peeing on him? He does sleep with his head under her bum a lot. I have only been noticing this once in awhile over the past 2 weeks

that's what I notice on mines after they groom each others

does seem a little wet for grooming.
I would check pouch for smell or wetness. if its already bad, you could wash it then check next time you see him wet. If its pee you will smell and feel the wetness. One of our new gliders wouldn't leave the pouch for the first few day and just peed in hammock. But after that stopped. I have seen some pee on outside opening of pouch a few times, think this was to mark the sleeping pouch.
But we probably pull down pouches once or twice a day to check on them and give them a head pet, or put one in a pouch, and I have NOT seen a wet head and ours do groom a lot. I have even had my head groomed a little and it's a dry groom like a cat.