First, in Washington, all of the property, both separate and community is before the court for purposes of dividing. Whether, however, the court would invade the separate portion of these accounts will depend on a number of factors. You will also need to separate out which portions are community and which portions are separate. You will probably need the help of an attorney or actuary to accomplish this. The fact that a third party is named as beneficiary should make no difference.
Your post implies that you are no longer married. When a person gets divorced retirement are supposed to be divided in the divorce decree. If you are divorced and your divorce decree did not give the retirement funds to anyone then you would have to request that they be divided in a post decree action.
Sometimes people accidentally divide the retirements without knowing I have done so.
The beneficiaries do not matter. If you are not yet divorced and what the other attorney indicated I agree with and you should consult a local attorney to make sure the division is fair and equitable.
First, I would post this under Divorce to get more traffic. Typically, what each had before is separate. The increase after marriage can be marital but that can get tricky. What II would do if I was you is consult in person with a divorce attorney in your area.