All the Osak worlds

I was watching Firefly and it hit me: how about two or three of these are habitable asteroids?  Say there's an asteroid field in the Osak system, right in the habitable zone of the star.  Say some of these are of sufficient size to actually have an atmosphere, decent gravity, etc.  That could explain four or five habitable worlds in the same G4 star system.  My other option is to make the osakar race able to live in a wider range of temperatures, atmospheres and conditions, some of which could be uninhabitable to non-osakar.