He wants to take her baby


My sister was with a guy and ended up pregnant. Then he decides to tell her he's getting back with his WIFE!! What!! This was a huge shock nobody knew he had a wife. A month goes by with very minimum communication between them and he starts threatening her out of the blue. Once a month he sends long texts explaining that hes going to get a court order to FORCE her give the baby his last name. He also says he will get full custody as soon as the baby is born and that he and his wife will be raising the baby.. Mind you my sister is by no means going to be an unfit mother. She has her own house a good job and doesn't do any drugs or drink. Hes been telling her she has to allow him to he there for delivery and to sign the birth certificate and that she better get a lawyer because hes fighting to completely take the baby away. Has anyone else dealt with anything like this and what did you do about it?