RCW 51.08.030: "Child."

"Child" means every natural born child, posthumous child, stepchild, child legally adopted prior to the injury, child born after the injury where conception occurred prior to the injury, and dependent child in the legal custody and control of the worker, all while under the age of eighteen years, or under the age of twenty-three years while permanently enrolled at a full time course in an accredited school, and over the age of eighteen years if the child is a dependent as a result of a disability.