I came out in December of 2014 and it was rejected by my parents as too young while all my friends were understanding. I think twelve may be a bit too young (but maybe not) because I didn't feel aro as an anomaly to everyone else but by 14 there was something unavoidable there. I came out again in summer 2016 (ironically while in Paris) and it was taken neutrally so whatever, at least my parents will know why nothing ever happens.