I originally rescued two gliders (both neutered males) and one of them died of a heart problem. The other male has been alone for almost 6 months, and a month ago we rescued a family of five! Two baby girls, the mom and unnuetered dad. I had to pull the babies out because they've reached the age of sexual maturity and I didn't want issues. I've introduced them to my neutered male and at first they all got along, for the whole two weeks of introductions on neutral grounds. I moved the girls into Meiko's cage and now he seems to be 'attacking' (for lack of a better word) the most dominate of the two girls. Is this something I should be worried about, or will they just have to work this out between themselves?

Introductions can always go well in neutral grounds but when you let the new gliders be in the care of a glider that was there 1st you are going to have to expect the older one that was there 1st to assert their dominance. Even though he is neutered it is still his cage. My advice is to check when you hear fighting and if it seems a bit much take the 2 that are having the conflict into the bathroom and let them spend some time in the neutral zone it should cut down on the fighting. That is what I do with my boys and they are both intact so I have to do this a bit more regularly. But it works and they don't hardly fight anymore too

If they are balled up fighting, then yes, it is serious and one or both of them will get hurt.

They were not balled up, they just were I guess bickering and establishing who was more dominant. The fighting has resolved and every now and then they will kind of bark at each other but for the most part they all three get along now!