What's wrong with you skinny people?

my bmi is in the healthy range luckly but like my whole family is over what and it isn't like they don't try its not there fault its just ppls bodies are differnt some ppl eat whatever they want but don't gain any weight and I know someone who is really skinny and she stays the same weight wen she eats junk food and gains weight feom eating healthy food its really weird but ya some people are hippacrets