I can relate to your issue, though I can't imagine the trauma of losing your family. I have a history of sexual abuse and those voices are familiar to me. I never really found a therapist to help me through it, but here is something I did that helped.

Mindfulness is very important. I told myself to remember that all of those voices are children. Even the voice of my abuser is a child, because it isn't actually the voice of my abuser, but a voice that I created mimicking the voice of my abuser when I was a child. I created all of these fragments as a way to cope.

I am not a child, I am an adult. While those children repeatedly endure the abuse, I do not, because I am an adult and in control now.

Whenever I would hear the voices, I'd become what I envisioned a healthy parent to be. A healthy parent would be supportive and authoritative and I pretended to be one until it felt like a new "normal". As a healthy parent, I mediated between the voices, I supported both the good and bad, and I tried to help them find common ground so they could all exist in some sort of dysfunctional balance. Eventually they had nothing left to fight about and they quieted down.

I don't think it would work for everyone, and the care of a therapist is very necessary, but it's what helped me get through it. I know how frustrating it can be when you have all of that going on in your head almost constantly.