Is it normal for a 9 week old puppy to growl?

I have a 14 week old miniature jack russell puppy and he is the sweetest thing, acts alot older then he is and very intelligent, he can sit, give paw, lay down and now roll over when told but i am getting increasingy upset with what i feel are just discrimating comments like he's a jack russell and he'll be yappy and snappy and apparantly according to my auntie he also showed aggression from an early age because he growled at himself in the mirror and a 9 week old puppy shouldn't even be growling? I personally think its nonsense and bear in mind she's not a lover of jack russell's anyway. My jack russell is fantastic in every way so far, i have 3 children which he loves and he is very well socialised, he loves going over to the school and getting fussed by all the kids, he rarely barks, when he has its at something he is scared of or unfamiliar with. I would really appreciate some comments as i feel that there is bit of breed discrimination going on.