I have a single glider on his own currently and I am considering introducing him to an already bonded pair. The pair are only slightly younger than he is and they are all about the same size. The trouble is, the male of the bonded pair is not neutered, and the single glider is. The pair have not had any joeys and neither parent glider is aggressive or pouch protective, but I still worry about introducing him.

Either way, I have to wait until his fur condition heals to do any further introductions, but has anyone had experience with this before? I planned on keeping them on separate, but It'd be nice to give my lone glider some company.

At the end of the day, it really depends on the gliders.

As long as there aren't 2 intact males, there should not be competition for the female (on a side note, none of my gliders are neutered -it is extremely rarely done over here, and the glider community is not huge either- and I never had any problems in my colonies nor heard of any in the french speaking community)

Whatever you choose, the usual advices are :
do not do quick intro,
1st mix their scents by switching pieces of fleece from one cage to another,
only after that do introductions in a neutral place (a bathtube is perfect), during the day, and one glider of the pair at a time, not both of them at once.

(that being said, my gliders spared me the work by introducing themselves during one night when the older boys escaped from their cage and entered the joeys one... I found the 4 of them sleeping in one pouch when I woke up in the morning... but I would not advise trying such a thing, I only mentioned it to express the fact that introductions are not necessarily such a huge deal, I actually think that most of the time, it's the stress of the human which brings issues)