(1) If a child has an acknowledged parent, a proceeding to challenge the acknowledgment of parentage or a denial of parentage, brought by a signatory to the acknowledgment or denial, is governed by RCW 26.26A.240 and 26.26A.245.

(2) If a child has an acknowledged parent, the following rules apply in a proceeding to challenge the acknowledgment of parentage or a denial of parentage brought by an individual, other than the child, who has standing under RCW 26.26A.405 and was not a signatory to the acknowledgment or denial:

(a) The individual must commence the proceeding not later than four years after the effective date of the acknowledgment.

(b) The court may permit the proceeding only if the court finds permitting the proceeding is in the best interest of the child.

(c) If the court permits the proceeding, the court shall adjudicate parentage under RCW 26.26A.460.