This is a family matter and the only solution to it is to communicate with your parents. Here, your sister is not responsible for whatever is going on, nor your parents are wrong. It’s just that she is a kid and needs nourishing love. You can communicate and disclose this feeling with your parents so that they also know where they are lacking and if their child is not feeling secure. Don’t ever hate your little sister for such actions of your parents, just make them understand and see what works better in everyone’s life.