Any adult or minor may be adopted under this subtitle. Any adult may petition a court for adoption. If a petitioner is married and the prospective adoptee is a minor, 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; is not competent to join in the petition; or is a parent of the prospective adoptee; and has consented to the adoption in accordance with this subtitle. If the petitioner is married and the prospective adoptee is an adult, the petitioner’s spouse may join in the petition. Before a petition is filed under this subtitle, a petitioner shall move for, and a court shall order that, a case pending under Subtitle 3 of this title be closed. If the marital status of a petitioner changes before entry of an order under this subtitle, the petitioner shall amend the petition accordingly.