My mother passed away. I lived at home with her to care for her my whole life. My brother was out of the house when he was 21. Advice?

I think this is being written in the 3rd party which is very confusing.

If your friend has been diagnoised with a Dementia he cannot sign a contract. He needs a lawyer.

IF it is the friend that you are caring for that signed over the entire inheritance the signature is not valid due to the diagnosis of dementia.
If it is you that got drunk and signed over your inheritance well...that was a pretty expensive drink.
IF it is the friend you can contact whoever is POA and they can look into this. But if you have no legal stance there is nothing you can do other than report it as Abuse of a disabled person.

Just read your profile. So, you are a friend of someone who is in this position. Your friend probably doesn’t have a case. Contact a lawyer for appropriate advice. I don’t think this forum will be able to give you advice without having any specific details.

You mentioned threats. What kind of threat? Even so, this situation sounds very sketchy to me. How was your friend being forced to get drunk? None of this posting makes any sense to me.

Nevertheless. I wish your friend well and I am sorry for his loss.

What do you mean you "signed them over?" It only matters what is in the will, or how the state divides assets. It doesn't matter what you signed unless you signed it with witnesses in a Law office (which a lawyer would not have allowed).
Who is the executor of the estate? Is there a will. That's all that matters.
See an Elder Law Attorney or a Trust and Estate Attorney with the will, or prepare to open probate for your Mother's estate.
Don't drink with enemies.