Washington Revised Code Title 26. Domestic Relations § 26.26A.615. Consent to assisted reproduction

(a) The woman or the individual proves by clear and convincing evidence the existence of an express agreement entered into before conception that the individual and the woman intended they both would be parents of the child; or

(b) The woman and the individual for the first four years of the child's life, including any period of temporary absence, resided together in the same household with the child and both openly held out the child as the individual's child, unless the individual dies or becomes incapacitated before the child attains four years of age or the child dies before the child attains four years of age, in which case the court may find consent under this subsection to parentage if a party proves by clear and convincing evidence that the woman and the individual intended to reside together in the same household with the child and both intended the individual would openly hold out the child as the individual's child, but the individual was prevented from carrying out that intent by death or incapacity.