If, after termination of parental rights as to a child, there is an open guardianship case, a petition for adoption of the child may be filed only as provided in this Part IV of this subtitle. Any adult may petition a juvenile court for an adoption under this Part IV of this subtitle. If a petitioner under this section is married, the petitioner’s spouse shall join in the petition unless the spouse: is separated from the petitioner under a circumstance that gives the petitioner a ground for annulment or divorce; or is not competent to join in the petition. A petitioner under this section shall attach to a petition: all written consents required under § 5-350 of this subtitle; or if applicable: proof of guardianship or relinquishment of parental rights granted by an administrative, executive, or judicial body of a state or other jurisdiction; and certification that the guardianship or relinquishment was granted in compliance with the jurisdiction’s laws; a copy of an agreement, if any, for postadoption contact; and a notice of filing that: states the date on which the petition was filed; identifies each governmental unit or person whose consent was filed with the petition; if applicable, states that a postadoption agreement was filed with the petition; and includes no identifying information that would be in violation of an agreement or consent. In addition to a copy of an agreement for postadoption contact, a petitioner shall file the original agreement under seal. If the marital status of a petitioner changes before entry of an order, the petitioner shall amend the petition accordingly.