IMO, you might have a pair. If you have 2, and 1 becomes aggressive towards the other fishes, but not towards the other firefish, they may be a pairing up. If you want more than 1 in a community tank you need 2 females and a male.
If you post a picture of the 2 I may be able to tell you if they are a male and female. The can be bred in captivity and they would bring some good $$$.