He should probably obtain a determination regarding the paternity of the child. He could possibly be responsible for an enormous amount of child support. It wouldn't make sense for him to admit paternity if it is not the case.
Adoption usually does require the consent of the biological parents.
The main consideration should always be: "what's in the best interests of the child"?
Sign up to receive a 3-part series of useful information and advice about child custody law.