Is it possible to separate two chinchilla. I assume they have been together for 10 months since they are brothers. Can you separate two of them from each other?
You can. Breeders frequently separate litter mates.
I, personally, lean towards keeping same sex litter mates who are bonded together, since then they can socialize with each other and keep each other company.
I've separated litter mates who have been together for some time before. Most of my show chins are weaned with their littermates, separated for show prep, and if not sold individually or put into breeding, repaired after they are shown. It's no big deal, just be sure to give them more of your attention to help with the sudden isolation.
They will not get depressed and they will be just fine. Like mentioned, just give them some extra attention while they are adjusting to being on their own.