I was wondering the same thing, also will momma miss the babies when they go to new homes? Not sure if we are keeping the babies, if not they will stay for 12 weeks. Can't imagine giving them up though
Our first family cat came from a family friend. When she and her brother were reintroduced a few months later they tried to attack each other. My guess is the other cat becomes a friend, or an enemy, but not really a family member.
I got a feeling that our cats thought that we are their dad and mom. Sometime, Brownie will lick my hubby like a cat. He might be thinking, "poor daddy, his skin cannot grow any fur. Maybe if I lick him hard enough, his fur might grow better".
After about 12/14 weeks old, when a mom cat would leave her babies to fend for themselves, cats start to lose 'family' feeling as they lose the smell of the nest. Siblings/parent/children raised together will be friends, but they do not know they are brother/sister/mother/son etc and will even mate if left unfixed. If separated they will soon forget each other and will need to be re-introduced if they meet. Same goes for parent cats/babies.
My parents have a cat that had two kittens. They kept the kittens and now both are full-grown adult cats. The mother wants nothing to do with her children, it's the strangest thing. If they try and play with her, she bats at them or just walks away.