Yes, you can. It's best to slowly introduce them - scent swapping, putting cages next to each other, etc. Most people recommend a 30 day quarantine with vet testing to make sure one doesn't pass any diseases onto the other. I personally never did that. But when putting two gliders together, you should do it in a neutral space. Do NOT just shove them into the same cage, because gliders can get territorial. Also, there is a change they will not get along and maybe even fight... Do it in a space that you can separate a fight if needed. Bring a shirt or gloves because you will get bit if this happens. It's not common, I'm just telling you so you can be prepared.
On another note, they are approaching the age where they can have babies. You cannot let them breed before 1 year of age, if at all. I recommend that you neuter him. If you can't then I don't really know what you should do. Gliders that are fertile will mate, and if they have babies too young, they likely won't survive due to immaturity, rejection, etc. Good luck!