8 week kitten joining 16 day old kits

My litter of three turned eight weeks on Friday. Their feral mom was released when they were 6 weeks old. That day, we brought a new stray in who delivered 4 kits that night. I have cages for the two litters but could not lock older kittens in unattended (one got her head through and stuck...too frightening!). Mom2 was not happy locked up either; she would not lay with her kits much even at three days old, she would lay by cage door wanting out(feeding well though...kits gaining great weight).
This week I started introducing mom2 to older kits so she could have more time out of cage. Some grumbling at first but by Friday they were sharing wet food at feeder. Late this morning mom2 moved ONE of her kits and was curled up nursing her...AND the three older kittens. Two of the three went to new home this afternoon. Does anyone know if allowing the remaining 8 week old kitten to join the other family could cause problems? Mom was even cleaning her this afternoon. I can only separate by locking mom back up. This kitten will be staying for at least another month.
Thanks for any input!
Sharon

Nay, I think it should go well, if there arent any other complications.  Like the mom preferring the older one before her own, or the older one bossing way too much.

They had already met, so there shoulnd be any health complications either. Ie, if there are, it is too late anyway.

So just go on, as long it feels OK for you and all other involved.  

Welcome to our Forums!

Good luck!

Big size difference between the kittens, that's what would worry me. Generally a week or two is okay, more than that the sizes is too much for the little ones who get pushed aside, or the playing is too rough. 

Just keep an eye on them, mum accepting the kitten obviously isn't an issue she sounds quite happy with it I'd just keep a close eye on kitten behaviours.