Legal Question in Family Law in Washington

Your premise is incorrect. At age 18, the "child" is an adult and there are no custody orders that apply. They may live with whomever and wherever they choose, and the parents are generally not obligated to support them any further, unless they are dependent adult children for whom the order of child support extends beyond their 18th birthdays or graduation from high school, whichever comes last.

Please Google RCW Title 26 or if this link works, go to:http://apps.leg.wa.gov/RCW/default.aspx?Cite=26