Washington Revised Code Title 41. Public Employment, Civil Service, and Pensions § 41.05.095. Coverage for dependents under the age of twenty-six

(1) Any plan offered to employees under this chapter must offer each employee the option of covering any dependent of the employee under the age of twenty-six.

(2) Coverage must terminate upon attainment of age twenty-six except in the case of a child who is and continues to be both (a) incapable of self-sustaining employment by reason of a developmental or physical disability and (b) chiefly dependent upon the employee for support and maintenance, provided proof of such incapacity and dependency is furnished by the employee within sixty days of the child's attainment of age twenty-six and subsequently as may be required by the authority, but not more frequently than annually after the two-year period following the child's attainment of age twenty-six.