What Happens if I Find Out a Child Is Not Mine After a Divorce?

 Posted on August 07, 2025 in Paternity

Finding out that a child you believed was yours is not biologically related to you is a tough emotional blow under any circumstances. But learning this after a divorce — when you may already be paying child support — can feel like a betrayal layered on top of injustice.

If you live in Illinois, and you are facing this kind of discovery, it is important to understand how the law treats parentage after divorce and whether you can change existing support obligations. A Rolling Meadows, IL family lawyer who takes an aggressive approach to pursuing client interests can help you understand what to do next.

Can I Stop Paying Child Support If the Child Is Not Mine?

Under Illinois law, you may still be legally considered the child’s father, even if you are not the biological parent. This is because the law treats parentage as a legal status, not just a biological fact.

As of August 2025, Illinois law presumes that a man is the legal father of a child if he was married to the mother when the child was born or conceived. That presumption carries legal weight unless it is challenged and rebutted in time. If you signed a Voluntary Acknowledgement of Paternity (VAP) or were named as the legal father in your divorce judgment, the law may treat you as the child’s father, regardless of DNA results. Whatever you do, do not stop paying child support without a court order. Otherwise, you could land yourself in serious legal trouble.

Can I Challenge Paternity After Divorce in Illinois?

Yes, but there are strict time limits. Under 750 ILCS 46/205, a man who believes he is not the biological father must file a petition to challenge paternity within two years of learning facts that would lead a reasonable person to doubt paternity. This law applies even after a divorce, but the window to act is narrow.

In most cases, the court will not set aside a prior paternity determination or support order just because you later discover you are not the biological father. However, there are exceptions. For example, if your ex-wife committed fraud or concealed material information during the divorce, you may be able to file a motion to vacate the parentage portion of the divorce judgment. This kind of post-judgment relief is difficult to get and depends heavily on the specific facts and timing.

Can I Sue My Ex for Lying About Paternity?

If your ex-wife intentionally deceived you into believing you were the father, and you suffered financial harm as a result, you may have grounds for a civil lawsuit for fraud. These cases are rare, and they can be emotionally grueling and difficult to win. Even if successful, a fraud suit may not relieve you of child support obligations, but it may allow you to recover some damages from your ex.

What Should I Do If I Just Found Out the Child Is Not Mine?

If you are in this situation, it is critical to speak with an experienced family attorney immediately. Timing is everything. Whether you want to challenge parentage, file a fraud claim, or understand your financial rights and responsibilities, you need guidance from someone who knows how Illinois courts approach these deeply personal issues.

Attorney Donald J. Cosley has spent over 30 years helping fathers throughout Cook County. When you work with him, you work directly with him, not a paralegal or junior associate. He will give you the honest, compassionate advice you need to decide your next steps.

Contact a Rolling Meadows, IL Paternity and Family Lawyer

If you recently learned that a child you supported is not biologically yours, contact an Arlington Heights, IL family law and paternity attorney at Law Offices of Donald J. Cosley to schedule a free consultation. Call 847-253-3100 today to protect your rights and understand your options.