How would my son inherit from my mother?

My stepfather passed away in 2016. My mother passed away in 2002 with a holographic will. My stepfather had none. My stepfather and my mother raised my son from elementary to high school. Would he inherit before anybody because my stepfather's half-brother took over and he's taken everything regardless of what my mother's will says? In my mother's will, she gifted us kids $150,000 shares from her company. My stepfather got the check but they say they can't find where he cashed it but in 2002 there was a bank deposit of $50,000 and who knows what he did with the rest. He could have bought a car too and they're not even acknowledging it. I also read somewhere that the holographic will is good for 3 years after it is acknowledged and that we could sue the estate for whatever he took from us that we didn't get. This probate case started June 30th 2016. I don't want this man to walk away with my mother's money.