[souffle]

That looks like mating behavior. The fact that one is so much larger is worrying. When the female is near to giving birth (and the large one does look quite round) they give out a scent that shows they are ready to mate again soon. They will mate immediately after the birth unless you remove the male and you get a second back to back litter. The fact the smaller one is cleaning his genitals straight after he stops perstering the other one makes me suspicious. That is what they do after mating or trying to mate. I'd like to see the underneath of them if possible. Can you pop the big one in a glass and take a pic through the glass. You can often see nipple lines on a pregnant female.