What can or should I do to get custody of my brothers?

I'm an 18 year old female and have 4 little brothers. One of them just turned 7 and requires special attention, he has a dad that has been trying to get custody of him. The middle 2 are 13 and 11 years old, their dad is in prison for raping me. (They're the ones m trying to get custody of). The last one is 14 and just recently moved in with his dad because our mom was abusing him. She was just convicted of a Class H felony child abuse. Her sentencing is on May 4th, 2018. She messaged me after she was convicted and blamed it all on me, and told me that my grandmother and I would never see or talk to my brothers again. She has abused me my whole life. Physically and mentally. She kicked me out of the house several times since I was 15 years old, not because I'm a bad child, but because my grandmother and I were calling social services on her. Shes now married to an abusive guy who has been charged with several battery crimes to his ex wives. Neither her, or her new husband have a job. He