Everybody's broodies are different, but mine would never tolerate being around other broodies. They're fine with non-brooding birds, but the moment two broodies are within sight of each other there's a fight.
One of my broodies has 2 chicks that are 24 days old, and they're old enough that they're living all day in a fenced-off area in the garden that's about 36 X 10 feet. That temporary fence is about 3 feet tall, and there's plenty to do in there so they stay put (so far). They'll be joining the main free range flock when they're big enough to no longer be a cat treat. My second broody has 13 chicks that are 14 days old. They've been living in the broody run in the barn, and yesterday I set up an outdoor run on grass for them. The temporary run is about 4 feet wide and 100 feet long, and uses the permanent garden fence as one of its sides. It is not anywhere near the first broody's run (about 75 feet away), but it is within sight. I needed to weight and evaluate and adjust the leg bands on all the chicks, which was difficult with mom in the pen, so I just did the first five chicks and took them plus mom out to the temporary run, then went back to the barn to work with the other 8 chicks. I was in the barn about 25-30 minutes, and when I came out with the other 8 chicks I found the two broodies fighting through the fence. Luckily none of the chicks were injured, but broody #1 had flown over her 3 foot fence and was trying to steal some of the 14 day old chicks, and broody #2 wasn't going to tolerate that. Luckily the chicks couldn't get through the fence, and the broodies couldn't seriously injure themselves, but they were totally exhausted and their faces were really bloodied.
So all my broodies are kept separate, starting on day one of the brood. It would be so nice to have communal brooding, but that just isn't going to happen with my overprotective girls.
Wow. Yea that definitely sounds like some major fighting.
So far I haven't had any bloody broody brawls. I've had multiple broodies with chicks before and usually the chicks stay close to their momma. But occasionally I'll get one that tries to switch camps and a small ruckus happens. But the silky moms have been good about maintaining the pecking order.