Short answer

If an heir who received an ownership share occupies the inherited property and refuses to leave or sell, you generally have four paths under Washington law: negotiate a buyout, use mediation, seek a court-ordered partition (sale or division), or pursue an action for possession/accounting of rents and expenses. Most heirs who inherit ownership become tenants in common (co‑owners) and each owner has the right to force a partition in superior court. Probate and property statutes in Washington affect the timing and process, so consult a local attorney early.

Detailed answer — legal framework and likely outcomes

1. How ownership is usually structured after a death

When someone dies and real property passes to multiple heirs (for example, by will or through intestacy), the heirs commonly hold the property as co‑owners (tenants in common) unless the will or deed says otherwise. Co‑owners each hold an undivided interest in the whole property. Washington probate law governs how title transfers during the estate process; see Washington probate laws for more on intestacy and distributions: RCW Title 11 (Probate).

2. Rights of an occupying heir who is a co‑owner

An heir who lives in the house does not automatically gain exclusive ownership simply by possession. As a co‑owner, the occupant has rights to use the property but also owes duties to the other co‑owners. Co‑owners can seek a court ordered accounting for rents or compensation for the period of occupation, and the court can apportion responsibilities for mortgage, taxes, insurance, and maintenance.

3. Partition actions — the usual remedy when co‑owners disagree

If heirs cannot agree about selling or dividing the property, any co‑owner may file a partition action in Washington Superior Court. A partition action asks the court to either physically divide the property (“partition in kind”) when feasible, or to order a sale and divide the sale proceeds among the owners. Courts generally prefer partition in kind only if it is practical and fair; otherwise they order sale. Partition actions and related civil procedures are governed by Washington civil procedure rules and court practice; see the Washington statutes and civil rules for court procedures: RCW Title 7 (Civil Actions & Procedure).

What the court can order in a partition case

• Partition in kind (rare for a single-family home unless land can be fairly divided).
• Sale of the property with proceeds divided according to ownership shares after paying liens, mortgages, taxes, and court costs.
• An accounting for rents, profits, and necessary expenses (the occupying co‑owner may have to reimburse others for fair rental value or pay contribution for expenses).
• Temporary orders about possession and preservation of the property while the case proceeds (e.g., to prevent waste or protect assets).

4. Possession and eviction issues

Because an occupying heir is an owner, standard landlord‑tenant eviction procedures do not apply. You generally cannot simply file a residential eviction against a co‑owner. Instead, ask the court in a partition or related action to resolve possession. In some cases, courts have ordered an occupying co‑owner to vacate or granted exclusive possession to another owner pending sale. The court may also direct that the occupying co‑owner be paid or charged for occupancy.

5. Probate administrator or executor involvement

If the estate is still open, the personal representative (executor/administrator) has statutory duties to manage estate property and may have the power to take steps to preserve estate assets, collect rents, and sometimes obtain court orders related to possession. After probate closes and title vests in heirs, the remedies shift to actions between co‑owners.

6. Costs, timing, and risks

Partition lawsuits can take months to years depending on complexity, title issues, and court schedules. The court may award costs and attorney fees to the prevailing party in limited circumstances, but each party should expect litigation expenses. Forced sale may yield less value than a negotiated sale, so many cases settle once the heirs understand the court’s likely outcome.

7. Practical alternatives often worth trying first

• Negotiate a buyout: one heir purchases the other’s interest at fair market value.
• Sell the property by agreement and divide proceeds.
• Use mediation or neutral appraisal to set value and terms.
• Agree to a timed buyout or listing period so one party has a fair chance to sell or refinance.

Statutes and official resources

Key Washington law resources you can consult include the state statutes on probate and civil procedure. Useful starting links:

• Washington probate statutes: RCW Title 11 (Probate)
• Washington civil actions and procedure statutes: RCW Title 7 (Civil Actions & Procedure)
• Washington Courts self-help and forms (civil litigation, probate): Washington Courts

Step-by-step checklist: what to do now

1. Confirm current legal ownership and how title passed (copy of deed and probate files).
2. Talk to the occupying heir. Offer a written buyout or sale proposal and set a reasonable deadline.
3. Get a professional appraisal or broker opinion of value so offers are realistic.
4. Consider mediation or neutral appraisal to bridge disagreements without court.
5. If negotiation stalls, consult a Washington real property attorney about filing a partition action in Superior Court.
6. Preserve evidence: keep records of payments, improvements, communications, and any rents or expenses paid by any party.
7. If probate remains open, inform the personal representative so they can protect estate interests.

Helpful hints

• Hire an attorney experienced in probate and partition litigation early. Partition law has procedural traps and local practice variations.
• Keep communication professional and document all offers and responses in writing.
• Don’t try to change locks or remove the occupant yourself—self-help can lead to legal trouble.
• Use neutral appraisal or mediation to reduce cost and emotional strain; courts often look favorably on parties who tried to settle.
• Check for liens, mortgages, and tax arrears before agreeing to buyout or sale; these affect net proceeds and obligations.
• If you fear property damage or waste, ask your lawyer about temporary injunctive relief to preserve the property pending suit.
• Get clear, written agreements when heirs agree to timelines, buyouts, or occupancy terms (who pays mortgage, utilities, insurance, and taxes while owner-occupied).