Legal Question in Family Law in Washington

A lot depends upon the age of the child and how the adoptive parents feel about it. Your best bet would be to begin with an informal agreement with the parents where he moves in with you, and nothing is said to any government agency. Then after the situation is stable, you could do something else more permanent. I would see if you could get the adoption vacated, though that would be difficult.

You should see an attorney for this because it would be important to map out a strategy and if the adoptive parents are not agreeable it would be much more difficult.