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All chickens are different and my backyard and coop is different from yours, etc. It's hard to compare.
However, my 2 1/2 year old Sussexes aren't good broodies at all. I have two. One went broody once this summer. She sat on the eggs in an old unused outbuilding. She had nothing to show for it when she came off the nest.
My Black Copper Marans, brown egg layers, I have about 7 of them, and quite a few went broody each summer. I can't remember how many I had hatch out chicks, but they can do it and raise chicks, too. I think about three have hatched chicks.
Problem: I haven't weighed the Black Copper Marans hens. I don't think there's any real chance that any of mine are over 7 lbs when adult since the French standard is 5.7 - 7 lbs. But who knows? They certainly aren't any bigger than my Sussex.