OK, Mum and Dad are fighting. What to do?

I’ve tried ignoring this for the past few years but it’s only getting worse. Mum and dad are constantly fighting and it’s not pretty. It often ends up in physical violence, and this scares me. I’ve tried to put this at the back of my head and not think about it but it’s not working. I need some help and advice on how to deal with it. It’s affecting me and my siblings and I’m really worried. My youngest sister is only two and she’s had to witness some nasty stuff.
What can I do?