Was it me or just my ptsd telling me I did it?

My life till 8 years old seem so normal and average, but then divorce happened so unexpected. My mom married my step dad and my dad married my step mom that's 4 parents and not even 1/4 could not abuse me in one way or another, I have no break I have no where to go. My step mom hates me and I don't know why. She would always hit me and throw things at me for just being "there" and my dad watched saying it was my fault. Till one day I was sitting at the table drinking water because it helped fill my stomach a little after my step mom would make me watch my sibling eat there meals while I got nothing and I heard her coming down the hallway, I made sure not to look up from my phone so she couldn't make up a lie saying I rolled my eyes when I never disrespected her in any way, but still as I looked down she started calling me a brat and disrespectful and I looked up and she threw a plastic cup at me and left as if she wanted a reaction, and yelled at my dad saying I was a b* and she hit him really hard and we left for 3 weeks until one day my dad went back to grab his stuff and she accused him of choking her and he went to jail. I saw his face so lifeless on the mugshot and I broke down, I missed the old him. I blame myself for my dad being in jail to this day telling myself that if I never went and drank water that she wouldnt have yelled at me n then my dad, or that if I was dead that this wouldn't have happened, but is it my fault or the ptsd talking? It's not fair my dads in jail suffering from me