Just the Law...
Under Washington law, wrongful death actions are strictly governed by statute. Atchison v. Great W. Malting Co., 161 Wn.2d 372 (2007). When the death of a person is caused by the wrongful act of another, the decedent's personal representative may maintain an action for damages. RCW 4.20.010.
RCW 4.20.020 defines the beneficiaries of such a wrongful death action. First, it specifies that the action is for the benefit of the spouse, state registered partner, or children of the decedent. Then it provides if the decedent leaves no surviving spouse/partner, or children, the action may be maintained for the benefit of parents, sisters or brothers who may be dependent upon the deceased person for support. This means that parents or siblings of a deceased adult person are not entitled to bring a wrongful death action unless the decedent supported them. Cousins, aunts, and uncles are not included at all in the class of persons who may bring a wrongful death lawsuit.
The wrongful death laws of Washington were first written in the 1880s. They sometimes result in extreme unfairness. Primarily for unmarried adults who had no children and did not support their parents or siblings.