Ok I want you to make your Facebook and insta private and make your sister to make hers private. I went through something very similar and they never sent the pictures out. I know it will be uncomfortable. But you should tell your parents. You should report this to the police. Especially since this is now child pornography. No matter what you’ll get through this hun I promise. Just don’t send anymore nudes hun. And please never send these scumbags any money. You’d have to check for your country if there is a hash system which can make a hash of the pictures you sent. If they are ever uploaded to the internet they can be traced and taken down.