And... floating around in the back of my head is that these kittens are Wicket's size, but they're supposed to be from the younger and scrawnier litter. I don't know if you remember, but the kitten Barkley killed, I thought was a lot bigger than the rest of the litter, and now I'm not so sure that this momma didn't steal a few of her sister's kittens. Remember the first momma had them up on top of that cabinet, and maybe a few fell off and were scooped up by this other momma, especially now that we know she's a super mom. Anyway, the only point in all that is they might be 5 months old.
Yeah, you got a valid concern there about who’s kittens they really are and how old they are. A while back my BIL had a bunch of related cats that were having litters of kittens all the time, and all their kittens ended up in one big batch and the mothers would just take time about going in and nursing them.
So you might do well to go ahead and neuter Brother and let him back out. That’ll be the cheapest way out too. Neuters are cheaper than spays.
I’ve had 2 mamas and 2 litters in the same box before and they all nursed both mamas and I’ve switched some before because one mama had too many and the other not enough (if that’s possible). My big 4 month old kitten will go lay down with the babies and pretend he’s one of them for some reason. It looks funny.
I can see why you are worn out, but I don’t think it will last much longer. They surely will have another month before a pregnancy could be a possiblity. Surely, she would be yowling like they do if she were in heat. That is hard to sleep thru, too.