My nephew is being withheld from my brother for blackmail. Can he file for emergency custody?

My nephew was born out of wedlock. Mother and Father are split. Mother is not letting Father have baby because Father will not give her money. (Father does not give her money because she does not spend it on baby, instead he buys baby the items he needs, and he has receipts to prove this.) He has proof of this via cell phone texts where she tells him he cannot have baby unless he gives her money. This is blackmail that she has done more than once. Because she is doing this and he has not seen the baby in several weeks, can he file for emergency custody? Is there anything she is doing by using the baby as blackmail that is illegal? There is currently no legal custody agreement as they are in the process of filing. Their verbal agreement is he gets the baby every Thursday to Sunday.