My brother used to hit me a lot, but my parent justifies it by his autism and schizophrenia. Was it still abuse?

By enabling the behavior, your parents are not advocating for your needs. Regardless of a mental health diagnosis, the behavior is not appropriate or acceptable. The parents have a role in providing a safe and nurturing environment for all the children under the roof. A large part of working with diagnoses such as autism and schizophrenia is by following a care plan established by a mental health provider. These types of plans can assist parents and family members towards correcting behavior while still having a safe living situation for all family members. Abuse can persist in many ways- emotionally, physically, financially, etc. Without support from your parents validating your needs and safety, it presents a harmful environment.

Yes, that is still abuse. Your brother hit you, disabilities and disorders are no excuse for mistreatment. His struggles should not give him an excuse to cause you pain. I am so sorry your parents are invalidating your experience by brushing it off on his conditions, you deserve support from them. I can empathize with your situation, my parents also invalidated my abuse experiences. However, with professional help and both of us willing to improve, they now understand that I went through pain and need support. I hope your parents will learn soon and be able to support you. Recovery from these experiences is very possible, and I wish you the best in your journey.