Your cat feels safe you, and believes you are successfully keeping the predators away from your home. This is why she believes her kittens will be safe with you, too.
Your home is also your cat’s home – she wants to bring her family together! Although cats are very territorial, this might change in the domestic and loving environment.
Maybe she’s trying to tell you something is wrong with that one kitten! If she does this for a couple of times in a row, you should consult your veterinarian.