My sister in law died in a car accident. She had two small children. The fater of the kids did not sign the birth certificate. Myself and her brother as well as another sister would like to have custody. We want whatever home is better for them. Does anyone know what we are up against. I know we have to go to court but do we have to try to inform the father. He beat the mother when they were together and he has been gone for 4 or 5 months now and is on drugs. He did call the day of the accident and want the kids but we did not let him. We have not heard from him again. I just would like to know if anyone else has had to go through this and can offer some advise.

We need to know the state, in general.
But you could all be in legal hot water simply for denying the father, and yes attempts need to be made to contact the father, and you will have future problems if he gets DNA ordered, even some years from now, and of course he can get sober and responsible during that time. So whoever wants the children really needs to hire a lawyer. Are you married to her brother? It isn't clear.

Was there a police report on the beating? Do you have proof he is on drugs?

The court will probably ask about the father and require he be part of the proceedings.

Yes the child's father will have to be notified and have to be able to try and get custody. You will need to have evidence that can be proved in court. Merely your opinion is not evidence. As Scott said, you will need police reports, and convictions in court. And things accepted as evidence