(1) A proceeding to determine whether a presumed parent is a parent of a child may be commenced:

(a) Before the child becomes an adult; or

(b) After the child becomes an adult, but only if the child initiates the proceeding.

(2) A presumption of parentage under RCW 26.26A.115 cannot be overcome after the child attains four years of age unless the court determines:

(a) The presumed parent is not a genetic parent, never resided with the child, and never held out the child as the presumed parent's child; or

(b) The child has more than one presumed parent.

(3) Except as otherwise provided in RCW 26.26A.465, the following rules apply in a proceeding to adjudicate a presumed parent's parentage of a child if the woman who gave birth to the child is the only other individual with a claim to parentage of the child:

(a) If no party to the proceeding challenges the presumed parent's parentage of the child, the court shall adjudicate the presumed parent to be a parent of the child.

(b) If the presumed parent is identified under RCW 26.26A.325 as a genetic parent of the child and that identification is not successfully challenged under RCW 26.26A.325, the court shall adjudicate the presumed parent to be a parent of the child.

(c) If the presumed parent is not identified under RCW 26.26A.325 as a genetic parent of the child and the presumed parent or the woman who gave birth to the child challenges the presumed parent's parentage of the child, the court shall adjudicate the parentage of the child in the best interest of the child based on the factors under RCW 26.26A.460 (1) and (2).

(4) Except as otherwise provided in RCW 26.26A.465 and subject to other limitations in RCW 26.26A.400 through 26.26A.515, if in a proceeding to adjudicate a presumed parent's parentage of a child, another individual in addition to the woman who gave birth to the child asserts a claim to parentage of the child, the court shall adjudicate parentage under RCW 26.26A.460.