Adult Adoption in Illinois: Consent, Steps, Effects

Published: October 29, 2026

Adult adoption in Illinois lets a person 18 or older be adopted in two situations. Either the adult lived in your home for more than two years in a row at any time before filing, or you are one of the relatives the Adoption Act lists, such as a stepparent. The adult’s consent is the only consent required.

Your stepson is 24. You have raised him since he was six, and the two of you want the law to say what the family already knows. Can you adopt him now that he is grown? Yes. The Illinois Adoption Act has a path for adults, and it leaves out several steps that a child’s adoption requires. Our guide to how to adopt a child in Illinois shows those steps.

Who qualifies for adult adoption in Illinois?

Anyone 18 or older can be adopted in Illinois if one of two conditions is met, along with the Act’s other requirements covered below. The first condition is residence: under 750 ILCS 50/3, the adult lived in your home for more than two years in a row before the petition is filed. The Act says “at any time,” and we read those words to mean the stretch can come from years ago rather than the two years just before filing. The second condition is family: you are one of the relatives the Act lists, the same list it uses for a related child.

The definition in 750 ILCS 50/1 lists the relationships that count. The relationship can be by blood, marriage, adoption or civil union:

parent, grandparent or great-grandparent;
brother or sister, stepbrother or stepsister;
stepparent or step-grandparent;
uncle, aunt, great-uncle or great-aunt;
first cousin or second cousin.

A stepparent who is still married to the adult’s mother or father is on that list. So is a grandparent. A foster relationship is absent from the list, so a family that took in a young man who is not a relative uses the two-year residence rule instead. The same list governs a relative adoption of a child in Illinois, where it also skips the home study unless the judge orders one.

If the stepchild is still under 18, our post on stepparent adoption of a minor in Illinois covers that path, which has its own consent rules.

Does the adult’s mother or father have to agree?

Under 750 ILCS 50/8, the only consent required for an adult adoption is the adult’s own. The adult’s mother does not have to sign, and neither does the adult’s father. In a stepparent adoption your spouse, the adult’s mother or father, joins you on the petition, as the next section explains. The Act requires no signature from the other parent.

Under 750 ILCS 50/12, the adult’s consent must be in writing and acknowledged, meaning signed in front of a judge or another person the court allows. The signed consent becomes part of the court file. The Act includes an optional consent form for the adult’s mother or father. It is used only if the adult chooses to ask for it; nothing requires it.

The petition, described in 750 ILCS 50/5, does not have to name the adult’s mother or father. It does not need to say anything about how either of them behaved. An Illinois appellate court said in 2022, in a case called In re Adoption of Konieczny, that accusations about a parent’s conduct have no place in an adult adoption petition.

The Act sets no rule requiring notice to the adult’s mother or father. A judge may still want them told. Whether to tell them about the case is a judgment call we make with you.

Who files the petition?

The people adopting, called the petitioners, file the petition. An adult adoption is one petition in the circuit court, with no separate case to end anyone’s parental rights first. Under 750 ILCS 50/2, a married petitioner or one in a civil union files jointly with the spouse or partner. The exception is a couple who have lived apart for 12 months or longer. When a stepparent adopts, the adult’s mother or father signs the petition as well. That parent keeps every right he or she already has.

A petitioner must have lived in Illinois continuously for the six months immediately before filing. A member of the armed forces qualifies after making Illinois home for 90 days. If your marriage to the adult’s mother or father has ended, Illinois law still lets a former stepparent petition to adopt the former stepchild as an adult. For that adoption the Act drops the six-month rule, and your current spouse does not have to join the petition. One of the two conditions above still has to be met. As a rule of thumb, the two-year residence rule is the way in for a former stepparent.

Do you need a home study, and do you have to go to court?

Illinois does not require a home study for an adult adoption. Under 750 ILCS 50/6, the investigation and the fingerprint check that go with a child’s adoption are skipped for a related child or an adult unless the judge orders them.

The Act does not set a separate hearing rule for adult adoptions. Before anything is filed, we tell you what to expect in court. Adoption court files in Illinois are sealed from public inspection, and the case appears on the court’s calendar without the family’s names.

There is no deadline to adopt an adult and no waiting period written into the Adoption Act, so the petition may be filed at any time. Under 750 ILCS 50/14, the judge may enter the judgment, the order that completes the adoption, any time after the adult has signed the consent. The six-month waiting period that applies to some child adoptions does not apply to an adult adoption. How long the case takes depends on the court’s calendar.

What goes in the petition, and where is it filed?

The petition is short. It gives:

your names;
where you live and how long you have lived in Illinois;
the adult’s name, sex, and date and place of birth;
the name he or she will carry after the adoption.

You sign it under oath. Under 750 ILCS 50/4, the petition may be filed in any Illinois county, so a family in Peoria, Tazewell, McLean, Knox or Woodford County can file close to home.

What does an adult adoption change?

The judgment changes three things: the name on the record if the family chooses, the adult’s legal tie to a parent who is not part of the petition, and inheritance.

Does the adult’s name change?

The petition states the name the adult will use after the adoption, and the judgment carries it. The adult may keep his or her current name or take yours. For someone born in Illinois, the State Registrar issues a new birth certificate under 410 ILCS 535/17, and it takes the place of the original. The court, the adoptive parents or the adopted adult can ask that no new certificate be made. For someone born in another state, 410 ILCS 535/16 sends the Illinois record to that state, which follows its own rules.

What happens to the adult’s mother or father?

Since January 1, 2025, 750 ILCS 50/17 has covered adults as well as children. When the judgment of adoption is entered, the mother or father who is not part of the petition is relieved of parental responsibility and loses legal rights as a parent. In the Act’s words, the adopted adult is “free from all obligations of maintenance and obedience” toward that parent. A parent who joins the petition, as the mother or father does in a stepparent adoption, keeps every right.

As of 2026, we have found no Illinois appeals court ruling on how the 2025 wording applies to an adult adoption. A judge cannot enter an order against a parent who was never given formal notice of the case, so the notice decision above matters here too.

What about inheritance?

After the adoption, the adopted adult inherits from you as your child if you die without a will. Your will or trust treats him or her as your child unless it clearly says otherwise. The Illinois Probate Act, at 755 ILCS 5/2-4, sets one limit. A person adopted after turning 18 who never lived with you before 18 inherits from you but not through you from your relatives. Inheriting through you means taking a share from your relatives, for example your parents or your brothers and sisters. A stepson who grew up in your home is unaffected by that limit.

In a stepparent adoption, or an adoption by a grandparent, aunt or uncle, the Probate Act keeps the adopted adult’s inheritance rights from the mother’s family and from the father’s family. In an adoption by someone outside the family, those rights end, except from a parent who died before the adoption. A will or trust can set its own terms.

What is the next step?

Call and tell us about the person you want to adopt, how long he or she lived with you, and how you are related. The consultation is free. Robert Parker leads our adoption practice and personally handles every case the firm accepts. Our Illinois adoption practice page describes the types of adoption we handle.

Call 309-673-0069 or use the contact page to set up a consultation.

Frequently Asked Questions

Can I adopt my adult stepson in Illinois if his father will not sign?

Yes. Under the Illinois Adoption Act, the only consent required for an adult adoption is the adult’s own. His father does not have to sign, and the petition does not have to name him or describe his conduct. Whether to give him notice anyway is a decision we make with you.

Do we need a home study to adopt an adult in Illinois?

No. The Adoption Act skips the investigation and fingerprint check for an adult adoption unless the judge orders one. The default is none.

Is it too late to adopt my stepson now that he is 35?

No. The Illinois Adoption Act defines an adult as a person 18 or older and sets no deadline to file. The residence test asks whether he lived in your home for more than two years in a row at any time before the petition. Years spent under your roof as a teenager can qualify. As his stepparent, you are also on the Act’s list of relatives, which is a second way in.

Does adopting an adult change his inheritance rights in Illinois?

Yes. He inherits from you as your child, and your will or trust treats him as your child unless it clearly says otherwise. Someone adopted after 18 who never lived with you before 18 inherits from you but not through you from your relatives. In a stepparent, grandparent, aunt or uncle adoption he also keeps his inheritance rights from his mother’s family and his father’s family.

Can the adopted adult keep his last name?

Yes. The petition states the name the adult will carry after the adoption, and the Illinois Adoption Act does not require a change.

Adult Adoption in Illinois: Can You Adopt Your Grown Stepson?