EDIT : JB, you have a male, a female and a sub adult.
My findings from over the years(while working at a LFS) and my personal experiences.
People with larger tanks(5' or more) can usually get away with 2 pairs(of the same or different species) if the anemones stay at opposite ends of the tank. But an anemone is a must in order to keep the pairs in their respective territories. But dont try it with maroons, they are downright evil.
If you want more than a pair of a single species, it gets tricky. The only way I have ever seen it work is when the group is purchased at the same time when they are all sub adult (not male or female yet) and this usually only works in large groups of 8 or more.
Successes I have seen were a tank with almost 30 perculas, a tank with a group of 5 ocellaris, a tank with a pair of percs and clarks and a tank with a pair of percs and ocellaris.
I ended up trying it with 5 three month old, tank bread onyx clowns from JJ about 5 years ago.
All went well for the first 8-10 months or so. The larger one became female and the second largest one became male. Then two more turned male, and the fights started. The two smaller males would fight(not damaging each other but chasing) non stop, and I mean non stop for a week before I decided one had to be removed. They fought so much they didnt even notice the net coming for them.
Peace lasted about a week before the remaining two males started going at it. Same result, removed the other male.
I now have 3 onyx clowns. A pair and a sub adult that they will not allow anywhere near the anemone. He hangs out in my flowerpot. The pair never does anything harmful toward him, but they dont like him. Hes like the annoying friend no one wants around. They all got along decently when there was no anemone in the system though.
They have been living just fine like that ever since.
EDIT 2 found a pic of the clowns when I got them
