how she have more babies

[Tatt2Python]

hey ok im confused i had a mother rat with her babies, babies r 3 1/2 weeks old and there hasnt been a male with her since a week befor she droped 14 babies, now this morning i go to feed her and babies and she is sitting on 15 pinks
Does anyone have any clue on what happened did she breed with one of her boys or?

[Rhasputin]

Female rats, and mice, can store sperm, and have several litters from one breeding.

I have a female mouse here that has done it 3 times. And another that has done it once.
Often, the stored sperm results in a smaller litter than typical.

It's also possible she bred with one of her sons, but they're so young, i couldn't imagine.