RCW 12.04.140: Action by person under eighteen years.

Except as provided under RCW 7.105.100, no action shall be commenced by any person under the age of eighteen years, except by his guardian, or until a next friend for such a person shall have been appointed. Whenever requested, the justice shall appoint some suitable person, who shall consent thereto in writing, to be named by such plaintiff, to act as his or her next friend in such action, who shall be responsible for the costs therein.