My brother signed the birth certificate of his girlfriends child. He passed away and it is being said someone else is the father. What rights do we have as the family of the person (my brother) who signed the birth certificate?

Depends of if what is being said is true or not.

Technically you don't have any rights now, although your parents can file for grandparent visitation if necessary to see the child.

What is the situation? I don't want to speculate. What is it that you are trying to figure out? Your question is very vague.

Where and what is your problem with all of this?

Is the child collecting SS benefits from your brother's account? Do you want to stop them?

You have no legal standing in this - your parents (as my colleague, Steve, said) may have some rights, depending on your State.

I am just wanting to know if my Mom has any custody rights? My brother may not be the father but he signed the birth certificate. There is no issue with SS benefits or anything like that. We just want to know how it will go if my mom wanted to get custody because right now the child is in DHS due to some underlying issue with the child's mother who is 16.

Your mother may be able to apply for guardianship, yes. She should contact DHS. As of right now, your brother is the legal father. DNA would have to be ordered by a court to disprove it and it doesn't sound like someone else is stepping up looking to take custody.