My daughter (4yo) was asking my wife about boobs one day because my wife was wearing a low cut shirt that exposed cleavage. My wife answered her and explained that all girls get boobs when they get older and become women. She also added that "men don't get boobs but they can grow beards like daddy" because we have a son (3 yo) also. My daughter replies with "Oh no mommy I have seen big fat guys with boobs" So now having "the talk" with kids is explaining what's wrong with fat people and why they do not look like their biological gender.