Legal Question in Family Law in Washington

This is always a difficult and frustrating situation. Usually for all concerned. As a matter of law, the 18 y/o is now legally an adult and is no longer subject to parental custody. As to the 15 y/o, there is no longer a basis for a custody decision to be made between two parents. Regardless of what a divorce judgment may have provided on the issue of custody between two parents, the situation now is that there is only ONE parent, and thst parent is you. Until and unless a court says otherwise, you are the sole parent of the 15 y/o and you now have full legal custody. From a legal perspective, parent has a natural right of custody of a minor child over any claim of a non-parent (and a stepparnt is a "non-parent"). Absent the most compelling of reasons, there is generally no basis for depriving an otherwise fit parent of the natural right to custody of the parent's child. Also, from a legal perspective, it is not the child's right to determine with whom the child is going to reside. Minor children are normally in the custody of a parent (rather than an non-parent), and it is generally not the child's choice to live with a non-parent.

Now, having explained the legal aspect, you should be conscientious as to the practical side of this situation. The remaining minor child is 15 years old. Forcing that child to now take up residency with you, particularly if the child does not want that to happen, is most likely just going to cause a lot of problems for everybody involved. Sometimes it is better to put practicality over legality. Perhaps you and the step-father, in cooperation with the 15 y/o, can work out an arrangement that would mutually agreeable and in the best interests of all concerned. Keep in mind that in less than 36 months, the 15 y/o will be an adult (at age 18) and will then be in nobody's legal custody.