I wouldn't attempt it, as even though the tank may hold many gallons, the surface is still limited and the risk of them often seeing each other is too great to risk, imo.
But I do believe that after multiple generations you can possibly get some siblings to live semi-peacefully together, it's still a risk in ways.
I honestly think that if every breeder worked at it, that in time, and many-many generations later, we could possibly remove some of the aggression out of them enough to be able to put a few in together in the same tank. There are some cichlids out there that can be feisty with each other, but as long as they have their own territory, can possibly live together without too much trouble. I think that it may be able to have that instinct withered down enough to allow small groups living together of both sexes. By keeping them/selling them separate and some encouraging that aggression, it is hindering that process.
Breeder so I have too many to count and too many named to list here!