I know from reading this section often that if the littlest guy can't seem to gain weight, or if you see him being pushed aside by the other kits when it's time to nurse, that you can rotate them. Take the two biggest out for 2 hours, then put them back and take the little guy out, etc.
Maybe that would be a good time to put them in with the father, he might cheer up if he gets to groom and sit with the little ones--I made the mistake of not separating Rodya and Sonya after she gave birth to Ivan, so I'm still waiting to see if she has another litter, BUT Rodya was an excellent father, he enjoyed grooming Ivan, and he would sit next to Sonya and they would tuck the baby between them to keep him really warm. If I would take Ivan out of the cage and he would make his little peeping noises, Rodya would often be the first to come to the front of the cage to see what was wrong. Unlike most rodents, Chins make great fathers
not like hamsters or something who often kill their young..
Anyway that's just *if* you need to rotate them, and that's just my suggestion based on one litter, so you should def wait until Tunes or Tabitha let you/us know whether my idea is a bad one, or not, before you do that.