When beardies are little (under 4 to 6 months old), they do really well together. The increase in competition for food triggers their "survival aggression" and they are far more active. You do have to be careful because hungry babies will eat anything-- including the toes & fingers & tails of their siblings!
Once hormones start to flow through beardie veins, they lose the ability to be with their siblings and need to be housed by themselves. Males, especially, are far too territorial to share a space with any other beardie. Older beardies will injure or kill each other-- even if they are related.
So babies are okay together, juveniles & adults are NOT.
Just wanted to clarify that for you.