I think that is the reason too - but there isn't that much difference between the two ages of kittens, and the older two are that bit more hardy. The other problem we have is that everyone ringing up seems to want females, and we only have male kittens. Sometimes people think that if they get a male they will spray and you can sometimes persuade people, but one of the ones wants a ginger female, apparently her cats dont like males, even though the only ones they have met were adults, so a kitten would be different. T'other hasn't responded to me, so I can't even try and persuade her