"Does" are usually included in lawsuits when the plaintiff isn't sure if anyone else is responsible for the wrongs being alleged, and this way they can do a simple amendment later on naming them by name once they find out their identity.
Used like this with your last name, it means that the plaintiff thinks that one of your relatives with your same known last name should also be sued once they find out their actual name.
Disclaimer: I'm only licensed in CA. Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
Washington is a community property state. Plaintiffs will normally name the spouse of the defendant and the marital community so that any judgment can reach community property. If the plaintiff does not know the spouse's name, or whether the defendant is married, the spouse is named as John or Jane Doe and defendant's last name. You don't say whether your case concerns a contract or some sort of a tort (like a car accident). If you were not married when the incident occurred from which the suit arises, the inclusion of John Doe has no effect. But if you were recently divorced, it is possible your ex may be a legitimate defendant and should be notified.
Plaintiffs will also include a John Doe if they believe there is another person who may be liable but that person's name is not known. However, because your last name was included, I would expect John Doe was included as your spouse.