My brother inlaw and wife are forever having snide comments about our kids...it's very petty stuff really but it really gets under my skin as there is so many things I could say about their kids but choose not to as it is down right rude.
I know my children are far from angels but they are mannerly and fairly easy going. They nearly always they get the blame if somethings gone wrong or there's been a fight over a toy. In fact, even if mine are the ones who've been kicked or bitten, the reply is usually (eg.) 'well, you should have given her the toy and she wouldn't have hit you'!!
Sometimes I think it might be a jealousy thing as their kids are usually the ones screaming with tantrums at family get togethers(not saying ours don't...note usually!)
It makes me so frustrated and I really don't want to get into a 'my child is better than yours' thing.