hahaha but thats adorable.
I have 5 gliders, two are completely bonded to me in the same way, so when the OTHER two had a joey, I would have to take her out separately so I could hand-train her before I found her a new home. When I did that, the two others would slam into the front of the cage trying to get my attention so I would know "WE ARE RIGHT HERE LET US OUT"
When the baby was really little, like up to 4 weeks OOP, I would let them all out at the same time and the two bonded gliders liked the little girl and gave her kisses etc (they were her older siblings ).But by the time she was 6 weeks oop she was fully furred, bigger and gotten her own scent, so the male started to get very aggressive, and luckily it didnt happen outside of her cage... one day the male was hissing and lunging at her through the bars of her cage.
Either way, for a few weeks I had to take the joey out to play alone, and she had gotten bigger so it was usually quite a long play time. All i can say is, yes your gliders will be jealous when you have one out instead of them, and it sounds like it might be harder on your little guy since he is all alone in his cage? if you are his only friend that could definitely add to his anxiety about sharing you. But, It wont hurt your bond as long as you get them out after you spend time with the others. Its good to try and do it while he is sleeping, but even if he wakes up and demands attention, ignoring your other gliders is not an option, obviously.
I would try to get him a friend if you plan to keep him for a long time (is he a foster?), and he should be much happier and much more willing to share you.