How can our mother get custody of my brother's unborn child?

My brother has been in a relationship with a woman who has 7 children. All of which have been taken from her, due to a mental disability. My brother is legally blind and lives in a facility that will not allow him to care for or keep the child there with him. My mother of sound mind and in good health does not want the child taken by the state. She lives in another and is willing to care for and raise the child. Her concern is if the baby actually is my brothers and what steps she is to take so that the child is not taken, for any amount of time by the state. My question is what process of action is my mother to take for custody of the unborn child? Thanks in advance.