Ok so I ended up getting a third glider unexpectedly. A friend of mine knew someone who didn't want theirs anymore. They didn't take care if him properly and what not but that's a different story! anywho I decided to take in this little guy BC he needed a better home. Turns out he's not fixed. He's about 7 months old. He isn't too old to get fix is he? I would really like to get him neutered otherwise he's going to end up being in a separate cage from my little girl. (I have another boy also but he's was neutered when I purchased him)

Not at all.
You can neuter him.

Yep. You can definitely neuter him