I can help you with this. I used to breed and have been through it many times.
The problem with cats is they cannot count. So, whichever mom is the head kitty (alpha) will try to grab all the babies for herself. She actually "thinks" SHE gave birth to all of them.
The two problems are the stolen kittens are not getting colostrum from their own mother and her milk will dry up she does not nurse.
You can keep both mother cats in the same nesting area and let them nurse each others babies. However, if Betty will not put up with that, take two of the babies out and put them with their own mother. Cat #1 will probably try go get them and bring them back. However, she cannot be in two places at once. So, when she leaves the nest, get one of her babies and give it to her. Keep repeating this until she gives up.......she will eventually.
Get a feliway plug-in to keep everyone calm.
Please let me know how things are going. If you need anything along the way, I will be here for you.
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