Formalizing Family Relationships Between Adults

Adult adoption is historically the oldest form of adoption, predating modern laws governing the adoption of minor children. For centuries, adult adoption was used to formalize family bonds, secure inheritance, and recognize parental relationships that already existed in practice—famously including the adoption of Octavian by Julius Caesar. Washington law continues this tradition by allowing one adult to adopt another adult, creating a permanent legal parent-child relationship.

Today, adult adoption is often used to formalize long-standing family relationships, provide legal clarity for inheritance and estate planning, or recognize parental bonds that were never legally established earlier in life. While adult adoption does not involve placement reports or child welfare investigations, it still carries significant and permanent legal consequences that should be carefully considered.

➡ For general information on adoption, see our page Adoption in Washington State

Common Myths About Adult Adoption

Myth: Adult adoption is only symbolic.

Adult adoption has real legal consequences. It permanently changes legal parentage and affects inheritance, family relationships, and legal status under Washington law.

Myth: Adult adoption does not require court approval.

Adult adoption still requires a court order. The court must approve the adoption and enter a final decree for it to be legally effective.

Myth: Adult adoption can be undone if circumstances change.

Adult adoption is intended to be permanent. Courts do not reverse adoptions simply because relationships later change.

Myth: Adult adoption affects only the adopting parent and adoptee.

Adult adoption can affect inheritance rights, existing family relationships, and legal obligations. Its effects extend beyond the two individuals involved.

Myth: Consent is optional in adult adoption.

Consent is required. Both the adopting adult and the adult being adopted must consent to the adoption.

Myth: Adult adoption requires termination of parental rights.

Adult adoption does not require termination of existing parental rights in the same way minor adoption does. However, it still legally establishes a new parent-child relationship.

Myth: Adult adoption is rare or discouraged by courts.

Adult adoption is permitted by statute and regularly approved when legal requirements are met. Courts focus on consent and legal compliance, not subjective family dynamics.

Who Can Adopt and Be Adopted as an Adult

Who can adopt an adult in Washington State?

Any adult may adopt another adult if statutory requirements are met and the court approves the adoption. There is no requirement that the adopting adult be married or related by blood. The court focuses on consent and legal eligibility. (RCW 26.33.040)

➡ For more information see Who Can Adopt in Washington State

Who can be adopted as an adult?

Any person age 18 or older may be adopted. The adoptee must voluntarily consent to the adoption. Adult adoption is not limited to stepchildren or relatives.

Does the adopting parent have to be older than the adoptee?

Washington law does not impose a specific age gap requirement. However, courts expect the relationship to make sense in context. Extreme age reversals may raise questions, but they are not automatically prohibited.

➡ Learn more on our page What to Expect in an Adoption Hearing

Legal Effects of Adult Adoption

What legal rights are created by adult adoption?

Adult adoption creates a full legal parent-child relationship. This includes inheritance rights and recognition as a legal child under Washington law. The relationship is intended to be permanent. (RCW 26.33.260)

How does adult adoption affect inheritance?

After adult adoption, the adoptee is treated as the legal child of the adoptive parent for inheritance purposes under Washington law. This can affect intestate succession and may alter who inherits if no will or trust is in place. Because adult adoption can change default inheritance rights, existing estate planning documents should be reviewed and updated as needed.

➡ Learn more on our page Estate Planning in Washington State

Does adult adoption affect existing family relationships?

It can. Adult adoption may alter legal inheritance rights within extended families. It does not erase emotional relationships, but it can change legal status.

How Adult Adoption Differs From Adoption of a Minor

Are background checks required for adult adoption?

No. Background checks and placement reports are not required for adult adoption. The court’s focus is on consent and legal compliance, not child welfare evaluation.

Does ICWA apply to adult adoption?

No. ICWA applies only to adoption cases involving minor children who are tribal members or eligible for tribal membership. Adult adoption is outside ICWA’s scope.

➡ Learn more on our page Indian Child Welfare Act (ICWA) and Tribal Considerations

Is termination of parental rights required?

No. Adult adoption does not involve termination of parental rights in the same manner as minor adoption. The legal effect is the creation of a new parent-child relationship, not the removal of an existing one.

Moving Forward With Adult Adoption

Adult adoption can be a meaningful way to formally recognize family relationships that already exist. While the process is generally simpler than adoption of a minor, the legal consequences are permanent and should be approached thoughtfully.

At Pacific Northwest Family Law, we help families evaluate whether adult adoption aligns with their goals and guide them through the process with clarity and care. If you are considering adult adoption, we invite you to take the next step.

Complete our contact form to begin the new client intake process and speak with our team about your adoption goals.

Reviewed by Attorney Zachary C Ashby, Pacific Northwest Family Law, February 2026