We had a 4 year old pregnant tortie hanging around and she used to sneak in the garage
whenever we left it open (Was just used for storage - no car) and one day she never showed
up to eat.

While putting stuff in garage one day we heard kittens and eventualy found Kitty (The
tortie) had her kittens in the attic of garage.  We kept the garage closed up then with a
litter box and food.  When the kittens were big enough for weaning we would feed them and
in the process Kitty would come and set off to the side and keep an eye on her babies.  As
time went on she would become more trusting and come closed and let us pet her.

We found homes for all six of the babies and had Kitty spayed.  After spaying we kept her
in house until she healed.  When she was better we would let her out at night when she
wanted and she always would be back and setting at the door whenever we checked for her
but as time passed she wanted out less and less.  When winter came she would stick her
head out when we opened the door but hurried right back in.  Now at 13 years old she is a
indoor only cat and never even goes to the door except when I come in after being gone.

I guess what I am trying to say is that is you could keep the mothers with the kittens
that maybe in the process of socializing the babies the mothers might tame down also.

Good luck to you and the kittens.