What Happens If I Establish Paternity and Find Out Later That the Child Is Not Really Mine?

 Posted on January 26, 2026 in Child Support

Finding out you are not the biological father of a child you thought was yours can be devastating. Depending on the situation, some fathers may choose not to allow this information to change anything. For others, it can be such a betrayal that they feel like they cannot continue to participate in their family in the same way.

In Illinois, this situation creates legal challenges because establishing paternity forms legal ties that are not easy to undo. Whether you signed a Voluntary Acknowledgement of Paternity at the hospital, got a court order, or were married when the child was born, the law treats you as the legal father until a court says otherwise.

If you are facing this difficult situation in 2026, our St. Charles family law attorney can help you understand your options and what steps to take next.

Can I Challenge Paternity After It Has Been Established in Illinois?

Yes, but in Illinois, challenging paternity depends on how it was established and how much time has passed. The process is not simple.

If you signed a Voluntary Acknowledgment of Paternity (VAP) at the hospital or with the Illinois Department of Healthcare and Family Services, you have 60 days from the date you signed to rescind it. After 60 days, the VAP becomes a final "legal finding of paternity." To challenge it after that, you must prove "fraud," "duress," or "material mistake of fact" under 750 ILCS 46/309. This means that you must prove that your partner was concealing the parentage for you or that you were wrong in assuming you were the father.

If paternity was established through a court order, you can file a motion to get rid of or modify the order. Bear in mind that Illinois courts say that the best interest of the child is the most important factor. This means even if genetic testing  shows you are not the biological father, the court might still keep you as the legal father.

What Does "Material Mistake of Fact" Mean for Illinois Paternity Cases?

A material mistake of fact is a serious mistake that affected your decision to sign the paternity acknowledgment. In paternity cases, this usually means you believed you were the biological father when you signed the form, but later DNA testing showed you were not.

To successfully challenge paternity based on material mistake of fact, you need to show:

• You had good reason to believe you were the father when you signed.

• You did not know anything that would have made you question paternity (for example, that your partner was seeing other people at the same time as you).

• Genetic testing now proves you are not the biological father.

• You acted quickly after learning the truth.

Courts look carefully at these cases. If you waited years to challenge paternity after learning you might not be the father, the court may decide you waited too long.

What Are My Rights and Responsibilities If I Am Not the Biological Father?

Even if DNA testing proves you are not the biological father, Illinois may still consider you the legal father. Legal paternity has obligations that do not automatically disappear when you learn you are not your child’s father.

As the legal father, you are responsible for:

• Paying child support.

• Following custody and visitation orders.

• Making decisions about the child's welfare if the court has told you to.

• Providing health insurance if ordered by the court.

You also have rights as the legal father. These include:

• Parenting time.

• Making decisions about the child's education, healthcare, and religion if the court says so.

• Access the child's school and medical records.

• The right to object to adoption or to the cutting off of your parental rights.

If a court agrees to remove you as the legal father, these rights and responsibilities end. However, this also means you lose the legal relationship with the child. In situations where you have raised the child and formed a bond, this may not be what you want.

Call a St. Charles Family Law Lawyer Today

Discovering you are not the biological father is life-changing. The laws around paternity in Illinois can be difficult to navigate on your own. Acting quickly is important because time limits may apply to your case.

Our Kane County paternity attorney has significant experience in family law and works as a mediator to help families find solutions when possible. When mediation is not the right path, our firm is willing to aggressively litigate cases in court when necessary to protect your interests. At Shaw Sanders, P.C., we understand how painful these situations can be and are here to guide you through your options. Call 630-584-5550 today for your free consultation.