It's hard not to love a kitten, even if you're a cat. In general, most adult cats will tolerate, if not show affection for, any kitten -- especially their own. But when those little fluff balls grow into full-fledged feline maturity, it's every cat for herself, and that includes mommy cats.
Mommy Cats Distance Themselves From Growing Kittens
Even the most standoffish cat will nurture and enjoy her own kittens -- up to a point. By the time her kittens are about 6 to 8 weeks old, a mommy cat, having accomplished the important work of teaching her kittens independence, will most likely begin to seek distance from the crew. She may seek out higher turf, keeping one eye on her growing cats from her perch on top of the sofa or a favorite chair. She'll still intervene if her babies are in trouble or get too rough in play, but she is less likely to interact with the kittens on a regular basis. She may even occasionally take a gentle swat at a youngster who disturbs her rest. This growing aloofness is normal behavior for mother cats as their kittens begin to grow up.
From the time a kitten reaches adolescence -- somewhere between 10 to 12 weeks -- a mommy cat may still tolerate his presence, and may even on occasion play with or show affection for her grown baby, but at this point, the relationship most often becomes one of kitty roommates. How well a mother gets along with her kittens will depend upon her temperament and her tolerance for sharing food, attention and space. At this point it's every cat for herself, and the familial relationship between a mommy cat and her kittens will not ensure harmony in the household. Kittens are ready to be separated from their mothers by this time and will thrive on their own in a new household. Mommy cats are unlikely to grieve for more than a day or two when their grown kittens disappear from the home. They may even seem relieved.
Helping Mommy Cats to Get Along With Their Kittens
If you have separated a mommy cat and her grown kittens for more than a day, you might be surprised to find her less than tolerant of their presence on their return. She may react to them as if they are stranger cats -- hissing, spitting or even swatting at them in anger. At this point, the best thing you can do to re-establish the peace in the household (and to protect the growing kittens, who can be traumatized by the mommy's aggressive behavior) is to isolate the kittens from their mother, putting them into separate rooms for a few days until she gets reaccustomed to their scent. Place the kittens' food bowls far away from the door separating them from the mommy cat, and then move them gradually closer every day until she has calmed down. At this point, reintroduce the grown kittens into the main living area of the home, but supervise the situation carefully until you see that mommy and her kittens appear to be getting along.
Enough is Enough
If your cat has moved beyond the aloof mommy phase and has become completely intolerant of the presence of her own grown kittens in the household, speak to your veterinarian about prescribing a short-term trial of behavioral medication for your cat. It is possible that your cat is suffering from anxiety or stress, and a few months on medication might help her to adjust to the idea of sharing her space with other cats. If you have tried various solutions, but your cat is still behaving aggressively towards her grown kittens, you may have no choice but to find the kittens new homes for their own safety (and your sanity).