Abusive Parents and Need Help

I am going to try and keep my story short. I usually don’t put my personal life out there too much but I need help and actually want to do something this time so that my siblings can have a better life than I did.

Ok so parents are very toxic people. They are sexist and my dad is abusive. When he gets angry he takes his anger out on the vulnerable kids. In this case, that was once me... But now it’s my youngest sister. (There are 5 of us). He beat me about twice in high school to the point where it left bruises, but after that it was maybe slaps here and there or just being verbally and mentally harassed almost every day. My mom sides with my dad and tells people that I’m over dramatic with my stories then will go on to tell them that her life was wayyy worse with her own dad and that my life was better than hers.

Now I’m older and out of the house but my 4 younger siblings still live with them. I’m super close with my siblings and only visit their house to be with them. Well I was just over at their house the other day, and my sister had told my parents before she went to school that day that she would only be going to school to work on a project that she’s really behind on... When the school called later that day and left a voicemail saying that she skipped classes, My dad told her to go in their room and he started beating her. I ran into that room as soon as I heard a loud bang and her screams. They had the door propped shut with something, so I wasn’t able to fully get in all the way but just enough to get my head and arm through. I saw my dad blocking my sister in a corner and my mom just standing there by the bed doing absolutely nothing. I yelled at him to leave her alone and he told me to shut my mouth and started to come at me. Only then did my mom try to stop him from coming at me because she knows that if they mess up with me I’ll leave forever because I’m sick of how they treated me in high school and only come around for my siblings.

The thing is, they don’t do this to my brothers. I could understand if it was one hit and if he disciplined all of us the same. But he doesn’t. She said that he punched her multiple times on the car ride home, then when they got home that’s when I was there and the whole extra beatings happened in the bedroom... My brothers can bring home bad grades, skip school, bring home girlfriends to meet my parents, have social media etc. But if me or my sisters were to pull half of what the boys in our family did, we get beat up for it. We love our brothers, like I said we are all so close as siblings. But my parents let the boys in the family get away with so much, while we as girls have to grow up thinking this is normal. That girls are objects or have certain rules that boys don’t have to follow.

It’s a super toxic household and I want to get my sisters out of it but I have no proof really. I never reported my situation to the police because I was so afraid when I was a teenager. Afraid that the police wouldn’t do anything and that my dad would beat me again if I put the cops on him. But I’m older and I want a better life for my sisters. I JUST DONT KNOW WHAT TO DO!! I want to report him and my mom to the cops but there’s not much proof. Will the police even do anything? Or will they just do a short investigation and if they find nothing, leave the kids there? My sisters might even be too afraid to speak out because if the authorities end up leaving them there they will pay for it from my dad.

Guys I need help and I’m sorry it’s long but if you read this and have any ideas on what to do, please help it will help me out so much.