Legal Question in Wills and Trusts in Washington

The law requires that all wills be filed with the clerk of the court after death--even if there is not a probate. So your sibling has an obligation to do so if he has the will. See RCW 11.20.010.

If he does not comply, you should see a lawyer.

This earlier answer is correct, as far as it goes. Once the will is filed with the county clerk, you may go the clerk's office and obtain a copy. If your sibling refuses to provide you with a copy and/or to file it, you will need the assistance of a lawyer and your sibling will likely be responsible for any resulting attorney fees.