If the "other man" is not merely listed on the birth certificate but ALSO signed an acknowledgment of paternity, then presumptively the child is legally his. As such, unless the mother plans on having the "other man" served with the custody papers, then she'll need to commence a paternity proceeding with the real father (& serve the "other man" with notice of that case). Call a Family Law attorney in your area for more info.  -- David Bliven, Westchester Family Law attorney (www.blivenlaw.net)