Can my husband adopt my son from a past marriage if the father will not consent

If your son is under eighteen and his biological father will not consent to the adoption, you would have to file a motion to terminate the biological father's rights to your son in order to move forward with any adoption.  Consult with a lawyer in your jurisdiction to see if the facts in your case qualify for bringing a termination action against your ex. If you are able to terminate his rights, your husband could move forward with requesting the Court allow him to adopt your son.