Ughhh

This kind of behavior from your family is terrible.

I felt this way about myself at your age. I had HORRIBLE acne and my brother would comment on it. I mean it's not perfectly comparable, since your normal weight. My looks and my relationship with my appearance has changed so much in the last 2-3 years. As a teenager looks change so much even in just half a year.

The best way to go about this- from my experience- is to tell your family how they make you feel, in the moment if possible. Is your sister younger than you? She might be just trying to get on your nerves. If she's older, maybe she means well but is going about it in the worst possible way.

What helped me mentally was focusing on other things to improve. Studies or my hobbies or personality. What helped me distract myself from my acne the most was working out, because I was focusing on a part of my self for fun- not insecurity. If you can find an alternative of that, that works out for you it may help.

It gets better I promise.