(a) Unless notice has been waived, notice of a proceeding for adoption of a child must be served, within twenty days after a petition for adoption is filed, upon:
(1) Any person whose consent to the adoption is required pursuant to the provisions of section 22-301, but notice need not be served upon a person whose parental relationship to the child or whose status as a guardian has been terminated;
(2) Any person whom the petitioner knows is claiming to be the father of the child and whose paternity of the child has been established pursuant to the provisions of 24-101, et seq.;
(3) Any person other than the petitioner who has legal or physical custody of the child or who has visitation rights with the child under an existing court order issued by a court in this or another state;
(4) The spouse of the petitioner if the spouse has not joined in the petition; and
(5) A grandparent of the child if the grandparent's child is a deceased parent of the child and, before death, the deceased parent had not executed a consent or relinquishment or the deceased parent's parental relationship to the child had not been otherwise terminated.
(b) The court shall require notice of a proceeding for adoption to be served upon any person the court finds, at any time during the proceeding, is:
(1) A person described in subsection (a) of this section who has not been given notice;
(2) A person who has revoked consent or relinquishment pursuant to the provisions of section 22-305; or
(3) A person who, on the basis of a previous relationship with the child, a parent, an alleged parent or the petitioner, can provide relevant information that the court, in its discretion, wants to hear.