Help me now or unborn kittens might die!?

I have been fostering cats and kittens for 5yrs now for our local animal shelter. currently I am fostering 2 females both at differint stages,Sophia is a new mom cat and has 3 baby kittens about to turn 2wks old and then momma cat who is going to be giving birth to kittens in about a week or 2. sophia is a very attentive great mommy who is protective yet very loving and friendly and momma cat who is my pregnant foster girl is very friendly and loving also but up until tonight sophia has been caring for her babies alone with my help in our family room in a medium size laundry basket. well tonight momma has taken a liking to sophia's babies she will not leave thier side which has made sophia appear depressed as she watches from the side line while another woman cares for her new babies.I keep taking momma out of the nest so sophia has room to get back in but she just jumps back in...I really dont want to put her another room because we are camping out in the family room so I can keep my eye on them due to both being labled "high risk" momma seeming she is about to give birth has milk and has been feeding sophia's babies and im just wondering if this is okay? I know humans first bits of milk is important for new baby and im wondering if this is the same for cats and if so then sophias babies are drinking the most nutrient filled parts of some other unborn kittens milk...if this is safe then I would love to just allow them to all be togather just so long as sophia is okay with allowing her babies to be shared with another woman "cat" I know they like each other and seeming they were homeless I hate to stress them, this is the only bit of security these cats have probably ever had. thanks is advance all advice will be appreciated