Burden of proof fallacy

Other than petitio principii, i found that my family members like to use Burden of Proof Fallacy when we are chatting.This incident happened when we was having dinner.
Father:"Do u think that you are putting on weight?"
I:"Really?"
Father:"Don't you think so?"
In that moment, I thought of critical thinking and i found that it is very useful to pursue or to argue with someone when one knows critical thinking.
After a few moment, my sis's turn to use Burden of proof Fallacy.
Sis:"Why are you so choosy when come to food?Why dont you eat everything mum cook?"
Brother:"Why should I?Why can't i eat whatever i like?"
Such a weird family i having!We like to use Burden of Proof Fallacy when come to chit-chatting.