Cartman's over here again. Guess he decided all the fuss over that lesser orange kitty was intolerable. ;-)
He just went under the house.
Maybe he's hunting mouses... He barely knows the other kitty is here. She's made eye contact with the other kittens, briefly, but he hasn't seen her yet.
If this momma is a week or more out, and she'll go crazy with boredom in that back room, I'd try to introduce them, but so far she seems rather content to be back there alone.
I think when we really think she's close, I'll lay out one of the rollaway beds and sleep back there with her. Otherwise, she's on her own and I'm not sure we'll know when she goes in to labor.
(we went through the same thing with the cats when the dog showed up. The big male Siamese whomped the poo out of the puppy, it didn't do her any harm and it DID engender respect. She will sniff his butt respectfully, but she won't chase him - not true wrt the other two cats. Although the youngest actually enjoys it - she runs up to the dog and "tags" her, then runs away.)