What to do about my family?

You do have a few choices, since your are 20 years old. You can move out. But it doesn't sound like your ready or want too. You know, you are not a little girl anymore. You are an adult. So I suggest that you sit down with your parents and talk to them. Even parents don't realize that their little girls suddenly grow up. Let them know that you love them. Tell them how you feel, and the reasons why you feel that way. I would not mention how you feel about your sister, because the conversation should be about you. Even if the talk does not go the way you want it, I will guarantee that your parents will think about the conversation and you will see some changes in their remarks and attitude towards you. You will also be planting a seed so that before they blurt something out that they might regret later, they will think first about what they want to say to you in the future. Make the conversation nice and let them know that you are sad and confused. Let them know that you feel lost right now and need their support. And about your sister, don't worry about how your parents treat her. They let her do things that you were not allowed to do because they learned from raising you. The first child usually is watched more carefully than the second child. They found out that you don't break too easily just like many other parents. They are just doing the best that they can. So cut them a break. Nobody is perfect, even parents. Good luck.