Why do big sister treat little sister's bad?

Big sisters may sometimes treat little sisters poorly due to a variety of reasons, including sibling rivalry, jealousy, or the desire to assert dominance. They might feel pressure to take on a caregiver role, which can lead to frustration and negative behavior. Additionally, they may be influenced by their own experiences and challenges in navigating their relationship with their parents and peers. Ultimately, these dynamics can vary widely based on individual personalities and family environments.