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.