Adult Adoption Illinois: Requirements, Process, and When It Makes Sense

Most people think of adoption as something that happens to children. In Illinois, it also happens to adults — and the reasons are more practical and more common than many families realize. A stepparent who raised a stepchild but never legally formalized the relationship. A foster family that maintained contact with a former foster youth into their twenties. An adult who was never adopted as a child but wants to establish a legal family bond now. Illinois law allows all of these, under specific conditions, and the process is considerably simpler than adopting a minor child.

The Statutory Basis: 750 ILCS 50 §2

Adult adoption in Illinois is authorized under the Illinois Adoption Act (750 ILCS 50 §2). The basic framework is straightforward: the adoptee must be at least 18 years old at the time of the adoption, and either a qualifying relationship or a period of cohabitation must exist between the adopting party and the adoptee.

There are two ways to satisfy the eligibility requirement:

Cohabitation: The adult adoptee and the prospective adoptive parent must have lived together for at least two years during the adoptee's minority — meaning at some point before the adoptee turned 18, they lived together for a continuous period of two years.

Relative relationship: If the prospective adoptive parent is related to the adult adoptee — stepparent, aunt, uncle, grandparent, or other familial connection — the two-year cohabitation requirement may be waived or more easily satisfied depending on the specific family circumstances.

The cohabitation requirement exists to ensure that adult adoption is used to formalize an existing, genuine relationship rather than as a mechanism for inheritance or immigration benefits detached from any actual family bond.

Who Consents in an Adult Adoption

In a standard adoption of a minor, the question of consent is complicated by birth parent rights, termination proceedings, and the 72-hour waiting period. Adult adoption is simpler on this dimension.

The adult adoptee must personally consent in writing. They are not a passive subject of the proceeding — they are an active participant with full legal capacity to consent or refuse. If the adult adoptee is married, their spouse's consent is also typically required.

The biological parents of the adoptee do not need to consent if the adoptee is 18 or older. Their parental rights were either already terminated as part of a prior adoption or simply cease to be relevant because the adoptee has reached majority. There is no requirement to locate, notify, or obtain consent from biological parents in an adult adoption.

If the prospective adoptive parent is married, their spouse must also consent to the adoption unless they are legally separated.

The Court Process

Adult adoption in Illinois proceeds through the Circuit Court, following the same basic procedural framework as minor child adoption under the Adoption Act.

Filing the petition: The adoption petition is filed in the county where either the petitioner (adoptive parent) or the respondent (adult adoptee) resides. The petition includes the identities of both parties, the basis for eligibility (cohabitation period or relationship), and the signed written consent of the adult adoptee.

Home study: Adult adoption does not require the same intensive home study that applies to adopting minor children. There is no Rule 402 physical inspection, no pre-service training requirement, and no post-placement supervisory period. The court still reviews the petition and may appoint a Guardian Ad Litem in complex cases, but the process is streamlined compared to adopting a child.

Finalization: If the court is satisfied that the statutory requirements are met and the adoption is in the interests of both parties, the judge enters a Judgment for Adoption. As with any Illinois adoption, a Report of Adoption is submitted to IDPH, which can issue a new birth certificate listing the adoptive parent.

Timing: Without the six-month post-placement wait that applies to minor child adoptions, adult adoption cases can move relatively quickly through the court — often 60 to 90 days from filing to finalization in less-congested counties, though Cook County's docket can extend that timeline.

Legal Effects of Adult Adoption

Once finalized, adult adoption in Illinois has the same legal effects as any adoption:

Inheritance rights: The adult adoptee becomes a legal heir of the adoptive parent. Unless specifically disinherited by will, they inherit as a child under Illinois intestacy law. Conversely, the adoptive parent becomes a legal relative who may inherit from the adoptee.

Name change: The adoptee may take the adoptive parent's surname as part of the adoption decree, or retain their original name — the choice is the adoptee's.

Severance of biological family ties: Adoption generally severs the legal relationship between the adoptee and their biological family. This means the adult adoptee is no longer a legal heir of the biological parents under intestacy unless the biological parent has made specific testamentary arrangements. This is a significant consequence that both parties should consider carefully with an attorney.

New birth certificate: IDPH issues a new birth certificate listing the adoptive parent. The original birth certificate is sealed, though the adult adoptee, as an Illinois adoptee aged 21 or older, retains the right under Public Act 96-0895 to access the original.

Common Scenarios Where Adult Adoption Makes Sense

Stepparent who never formalized the relationship: Perhaps the stepparent was unable to adopt during the child's minority because the biological parent refused to consent. Once the child turns 18, their own consent is all that's needed — the biological parent's refusal is no longer a barrier.

Former foster parent and foster youth: Foster youth who aged out of the system often maintain close relationships with former foster families. Adult adoption formalizes that bond and creates legal inheritance rights that foster care status alone does not.

Reconnection adoptions: An adult who was adopted as an infant, has now found and built a relationship with a biological parent, and wishes to be legally re-adopted by that parent. Illinois law does not prohibit this, though the legal consequences — including severing ties with the existing adoptive family — require careful consideration.

Estate planning alignment: Families using trusts or specific estate structures may find it legally cleaner for an adult child (by relationship but not by law) to be formally adopted to align legal status with the intended beneficiary structure.

What Adult Adoption Does Not Fix

Adult adoption in Illinois does not affect existing child support arrears, Social Security benefit calculations based on prior family structures, or most immigration status questions (which are governed by federal law and generally require adoption before age 18 for derivative citizenship purposes). If immigration status is a motivation, consult an immigration attorney before proceeding — adult adoption is unlikely to achieve what you're hoping for in that context.

For the full procedural checklist — petition filing, consent execution, and post-finalization IDPH steps — the Illinois Adoption Process Guide covers adult adoption alongside all other Illinois adoption pathways.

See more United States guides →