There is some debate about a suitable age for kittens to go to their new homes. Pedigree kittens tend to leave at about 13 weeks, after a course of vaccinations. If the breeder is good and understands that the responsibility for making a friendly and confident pet lies with him or her during the kittens first few months of life, (see bringing up a litter of kittens: behavioural considerations) then this should give the kittens every opportunity to learn positive lessons for the future.
If this is an unexpected litter of kittens, you may wish to find homes a little sooner. If your kittens appear happy and healthy you could consider allowing them to go a little sooner, from eight weeks onwards once they are fully weaned.
The transition to the new home should represent as few changes for the kitten as possible so it would be advisable to give the prospective owners information regarding your kittens’ current feeding regime and the litter material and tray type that they have been using. Familiar objects will be comforting for the kittens so sending them to their new homes with their own bedding and toys may help the settling in process. You should keep records of the worming and flea treatment that you have administered to pass to the new owners and you may also like to give them some information leaflets from your vet about vaccination, pet insurance (you may be able to give the new owner free insurance for their kitten for the next 6 weeks or so by contacting pet insurance companies) and any other useful advice that will help them have a long and happy relationship with their new cats. All of this information is available on this site and can be downloaded free of charge.
Some people feel they need to keep one of their female cat’s offspring rather than home all the kittens elsewhere but this isn’t necessary. She has been a great mother no doubt but, once the weaning process is complete, she has no desire to continue living with her kittens and will adjust well to being on her own again.
Don’t forget however that, once the kittens are weaned, your cat will come into season again quickly so ensure you have made the necessary appointment with your vet for her to be spayed (see neutering your cat or kitten).