maybe he was the last in his litter, they often vary in size.
Is he skinny or just small? If he is not skinny i would not worry to much as long as he is healthy.

about the 10 weeks guidelines...

i would not generalize it.
- many cats stop feeding the kittens before that already so the breeder has to nurse them.
- depending on the mothers blood type they have to take away the kittens from the mother anyway.
- most kitten 8-10 weeks eat baby cat dry food already.

Also many people had a good experience with younger kittens starting with 6-7 weeks as they will attach quicker to humans as you nurse them than a kitten who is 10 weeks and often older as those are more used to the other cats than human and often take much longer to get used to human.
With a social cat i don't talk about a Bengal who will play with you but will hardly let you pet him, hold him and so on. I hardly call cats who sit 1 months under your bed socialized. (adult cats yes but not kittens)

Of course i think it is a great idea to say that in general people should not sell before 10 weeks as most people have no clue about nursing young babies and maybe even would be to lazy to get them to a vet for a checkup and injections. But if you know your breeder well and he trusts you with the kitten knowing you will provide the baby everything its fine IMO.

i got my first 2 cats at the age of 5 and 6 weeks, they are both notorious lapcats with picture book behavior. Maya i got with 9 weeks and my latest one will get day after tomorrow with only 5 and half weeks.

_________________
Carol Goodall

"People that hate cats will come back as mice in their next life!"