Well I know that it's ok for moms to share babies. I only have one 3 shelf rat rack in two of those each time they give birth the moms find their corner and keep their separate from the other Which I like like this I does not matter how big or small the babies are they all get milk. But I have one that no matter what size they are they are all together like I had rat pups two weeks ago and more just yesterday I don't know if the big ones let the babies drink so what should I do? I got two more moms about to pop in that rack any day now