Quote Quoting Missouri Rules of Civil Procedure, Sec. 95.03. Petition for Change of a Minor's Name - Notice to or Consent of Parents
When a minor files a petition for change of name the written consent of each known parent shall be filed. If the written consent of each known parent is not filed, a copy of the petition together with a notice stating the date of the hearing shall be served on each known parent not consenting not less than thirty days before the date of the hearing. The service shall be by registered or certified mail addressed to the last known address of the nonconsenting parent. Service shall be proved by the certificate of the clerk that he has mailed a copy of the petition and notice by registered or certified mail.
No definition is provided for "known parent". I don't see any authority that indicates that a putative father is not a "known parent", but the language used suggests to me a broader intent than "legal parent". If you have retained a lawyer in your state who has informed you that the courts don't require notice to a putative father, even if you know him to be the father, I'll defer to your lawyer.