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If they were married he has as much right to the child as she has. I would strongly recommend that she get started on a immediate hearing on temporary custody of the child. If income is a issue, she can get in contact with Legal Aid Society as they can give her free legal assistance based on her income.
He had no right to throw her out of the home, even if he lives with his parents. If she would like she can sue his parents for a illegal eviction as well.
Keep in mind since they are married whomever has physical custody of the child (Is holding the child or has the child with them). The police can not intervene. If she can get the child for a short amount of time the police will allow her to leave with the baby.
Also if he works or leaves the child with his parents she can ask the police to escort her there to get the child since she is the mother. The police will allow her to take the child as long as dad doesn't have him/her with him.