Mother cat leaving home because of gown up kittens

Question
My first cat (Petra) had two litters, we kept one kitten from each litter. Petra doesn't get on with the kittens now they have grown up, and is increasingly agressive to them, and often leaves home for days even a week at a time. I'm afraid I will lose Petra. What can I do to encourage Petra to stay home and accept living with her kittens?

Answer
Ursula,

Cats have no concept of family. Once the kittens are grown the mother does not recognize them as her babies. Petra may be leaving home because she is in heat. The best thing to do to have any kind of harmony is to get them all spayed and neutered.

Tabbi