From what I can gather it should be fine, as the critical range is the first 2 weeks where you shouldn't handle them. Seeing as they're older than that and are big enough to run around rubbing up against the 4x 6 month olds, it should be ok. So long as momma doesn't mind.
I am very mindful not to get Furrball's scent on them, which is why I escorted the one out of the house. It might help that I've essentially spent the last 5 months integrating into their pride being rubbed on by 5 cats.
In other news, Mystic is more than twice the size of the 6 month olds and a former tom that'd get into fights that'd lead to bloody abscessed wounds. It's amusing to see him now regressed into literally playing with the others like a giant kitten, even trying to pounce and play, but due to his size he startles them. He's trying though.
I guess that's better than him trying to mate with Sadie and Sunnie when they were only 10 weeks.
- I forgot I didn't post this alternative to one I did post.
Okay sorry I need a census! You have Cinder, Mystic, and who as permanent guests?