Short answer

Yes — heirs of a deceased sibling can be included in a partition action in Washington when the deceased person owned an interest in the property at the time of death that passes to heirs. To add them you must identify the heirs (or the estate), name them or the personal representative in your pleadings, properly serve them, and ask the court to join them. The exact procedure depends on how title was held (tenancy in common vs. joint tenancy), whether a probate is open, and whether any heirs are minors or unknown.

Detailed answer — how Washington law treats heirs in partition cases

Partition actions in Washington involve dividing or selling real property among people who have ownership or claimed interests. Washington’s partition statutes set the court’s power to resolve rights and divide property among the persons interested. See the Washington partition statutes: RCW Chapter 7.28 (Partition).

1. Who must be joined in a partition action?

The court must include all parties who have a present ownership interest or a claimed interest in the parcel. If a sibling who owned a share died before the action, whether their heirs must be joined depends on how title passed:

• If the decedent owned as a tenant in common, their undivided share passed to their heirs or devisees. Those heirs (or the decedent’s personal representative/estate) are necessary parties to a partition action because they hold the decedent’s interest.
• If the decedent held as a joint tenant with rights of survivorship (or as community property with rights), the surviving joint tenant(s) may automatically own the decedent’s share, and the decedent’s heirs may not have an interest to be joined. You must check the chain of title and how the deed names owners.

2. How to determine who the heirs are

If the decedent left a will or an open probate, the personal representative will know who inherits. If there is no probate and no will, heirs are determined under Washington’s probate/intestate succession laws. See: RCW Chapter 11.04 (Intestate Succession). Typical steps:

1. Search for a probate or will in the county where the decedent lived and where the property is located.
2. Obtain the death certificate and any recorded probate documents (letters testamentary or letters of administration).
3. If no probate exists, investigate family records and public records (birth, marriage, funeral notices) to identify heirs under the intestacy rules.

3. How to add heirs or the estate to the partition case

Common ways to bring heirs into the case:

1. Join the personal representative or the decedent’s estate: If a probate is open, name the estate or the personal representative as a party. The personal representative is the proper party to represent the decedent’s interest in litigation while probate is pending.
2. Name the individual heirs: If no probate exists and you have identified heirs, add them individually to the partition complaint or by filing an amended complaint or motion to join necessary parties. The complaint should state each person’s interest (or claim to an interest).
3. Substitute parties when someone dies during litigation: If a named party dies after the action begins, you may need to substitute the personal representative or heirs under the court rules for substitution of parties (procedural rules govern this step in superior court).
4. Use publication or alternative service if heirs are unknown or cannot be located: If you cannot reasonably identify or locate heirs, the court can allow substitute service, such as publication. The court will require proof of reasonable efforts to locate missing heirs before permitting publication or other nonpersonal service.

4. Practical filing and service steps

Practical checklist to add heirs:

• Amend the complaint to add names and describe the interest, or file a motion joining additional parties as necessary.
• File a supporting declaration showing how you located the heirs or why the estate/personal representative is being joined (include death certificate, probate filings, chain of title).
• Serve each newly named party according to Washington service rules: personal service, summons by certified mail, or court-approved alternative methods (publication) if you cannot find them. File proofs of service.
• If minors or legally incompetent persons are involved, ask the court to appoint a guardian ad litem or to require a guardian/conservator to be joined to protect their interests.
• If title documents show survivorship, include documentary proof and ask the court to decide the effect of survivorship language on who must be joined and who owns the decedent’s share.

5. What happens after heirs are joined?

The court will determine each party’s interest and may order partition in kind (divide the property) or partition by sale with proceeds distributed according to the determined ownership interests. The court can also quiet title questions that affect who should be on title.

6. Special issues to watch for

• Title form matters: joint tenancy vs. tenancy in common vs. community property can change whether heirs have an enforceable interest.
• Open probate vs. closed estate: joining the estate or personal representative may be required while probate is pending.
• Unknown heirs: the court may permit service by publication only after you show diligent search attempts.
• Minor or incapacitated heirs: the court will require protective steps (guardian ad litem or guardian) before distributing proceeds or changing title.

Helpful hints — practical tips for litigants

• Start by examining the recorded deed: identify whether title names joint tenants, tenants in common, or others. That usually answers whether heirs inherit.
• Search for a probate case in the county where the decedent lived and where the property sits. If probate exists, use the estate/personal representative as the party for the decedent’s interest.
• Gather a certified copy of the death certificate early — courts commonly require it when adding an heir or estate.
• If you cannot locate heirs, document your search efforts (contacts with relatives, internet searches, public records) before asking the court for alternative service such as publication.
• If an heir is a minor or incapacitated, move promptly to have a guardian ad litem appointed or to join an authorized representative to avoid delays in distributing proceeds.
• Consider a title review by a title company or attorney to confirm how ownership would pass and whether a quiet title claim is more appropriate in some situations.
• File clear pleadings: say whether you are adding heirs as defendants claiming an interest or adding the estate/personal representative as the proper party in interest.
• Track and file proofs of service carefully; improper service can delay the case or require restarting the joinder process.

Where to find Washington law and forms

Primary statutory resources:

• Partition statutes: RCW Chapter 7.28 (Partition)
• Intestate succession (who are heirs): RCW Chapter 11.04 (Intestate Succession)

Local superior court clerks’ offices can provide procedural forms and filing guidance. Court rules and local rules control service, joinder, and substitution practice.