If they're related and have always lived together, it's possible they could live out their days in harmony without ever being neutered. It's not unheard of. Whether they do or not depends on your gliders.
Many recommend neutering because unneutered gliders living apart from females can become sexually frustrated and harm themselves, and unneutered gliders are more aggressive and could harm themselves or the other, but again this depends on the glider. If they've always been together then the chances of conflict are much lower, especially if they're both already mature and have established their pecking order.
If your boys aren't having any problems then I wouldn't worry too much about them. Just keep an eye out for any self-mutilation or aggressive/dominating behavior resulting in injury or stress. If that happens neutering may be in order, but if they are having no problems they're probably fine as is. If this does ever happen and you end up neutering try to get pom off neuters, pom on leaves them with some male hormones and behaviors and won't help as much.
How old are they and how long have they been together? If they're both mature and getting along then they'll probably continue to do so, although sudden squabbles among longtime cagemates are still possible even among neutered males.