Paternity When the Husband Is Not the Biological Father

 Posted on May 22, 2026 in Child Support

When a child is conceived or born while a woman is married, Illinois law presumes that the husband is the legal father of the child. In some cases, the husband is not the biological father, possibly because of adultery or a relationship prior to the marriage. If you are the presumed father of a child that is not yours, you may want to free yourself of any financial obligation to the child. Getting divorced will not change presumed paternity, but there are legal processes to establish the biological father as the parent.

At Calabrese Associates, P.C., we understand how stressful a paternity case can be. Our Naperville, IL family law attorney has decades of legal experience, so you can trust him to provide you with strong counsel and representation in court.

When Is Paternity Presumed in Illinois?

As previously mentioned, the husband of the mother is usually presumed to be the child’s legal father. However, paternity may also be presumed when the child’s mother and another person were in a civil union or a substantially similar legal relationship. This can apply if the child was born during that relationship or if the child was born within 300 days after the relationship ended.

This presumption can matter even if no DNA test has been done yet. The law may treat that person as the child’s legal parent unless the presumption is challenged and overcome in court. A presumed parent may have rights and duties, including the duty to support the child.

What Is a Denial of Paternity in Illinois?

If both you and your wife acknowledge that the child is not yours, you can sign a Denial of Paternity form within two years of the child’s birth. The form, which is filed with the Illinois Department of Healthcare and Family Services, states that:

• The presumed father is waiving all rights and duties as a father.

• The parents can rescind the Denial of Paternity within 60 days of it going into effect.

• The Denial of Paternity is only valid if the biological mother and father sign a Voluntary Acknowledgement of Paternity form.

• By signing the Denial of Paternity form, the presumed parents are giving up their right to genetic testing.

If the biological father cannot be found or you cannot prove he is the father, you may remain the presumed father.

What You Can Do to Challenge Paternity in 2026

If you do not agree on paternity, you can take your wife and the suspected biological father to court. The surest way to prove parentage is to demand genetic testing. The suspected father can refuse the test, but the court may then conclude that he is the father. Once paternity is established, the court will decide on the allocation of parental responsibilities, including parenting time and decision-making. The court will also address child support payments that each parent must contribute.

How Long Do You Have To Challenge Paternity in DuPage County?

The deadline to challenge paternity depends on how paternity was established. If a person signed a Voluntary Acknowledgment of Paternity, he or she generally has 60 days to rescind it. This means the person can cancel it by following the proper legal steps. After 60 days, the acknowledgment becomes much harder to challenge.

After that deadline, a challenge usually must be based on fraud, duress, or a material mistake of fact. In most cases, the person must file within two years after learning about the facts that support the challenge. For example, if a man finds out later that he may not be the biological father, he should act quickly. Waiting too long can limit his options.

A presumed parent may also face strict timing rules. If paternity is presumed because of a legal relationship with the child’s mother, a challenge usually must be brought within two years after the person knew or should have known about the facts showing that he or she may not be the child’s parent.

In DuPage County, paternity cases are handled through the family court system. A judge may look at the child’s age, the timing of the challenge, prior court orders, and the relationship between the child and the presumed or legal father. A DNA test may matter, but it may not automatically end legal parentage. Acting early can help protect your rights.

Maintaining Paternity When You Are Not the Birth Father

You may decide that you still want to be the child’s father, even if you are not the biological father. As previously mentioned, you are the child’s presumed father if you are married to the mother at the time of the birth. However, the biological father has the right to establish paternity and request allocation of parental responsibilities. If the biological father has no interest in being a parent, he can waive his parental responsibilities by allowing you to adopt the child.

What Do Courts Look at Before Terminating a Biological Father’s Parental Rights?

Terminating a biological father’s parental rights is a major legal step. Courts do not do this lightly. In many cases, this issue comes up when a non-biological parent wants to adopt the child. This may include a stepparent adoption or another family adoption.

The court may consider whether the father has maintained a relationship with the child. This can include visits, communication, support payments, and efforts to be involved in the child’s life. The court may also look at whether the father abandoned the child, failed to show interest, or failed to take responsibility.

Even if the court finds legal grounds to terminate rights, the child’s best interests remain central. The judge may consider the child’s safety, stability, emotional needs, bond with the adoptive parent, and current home life (750 ILCS 5/602.7). The court will also consider whether the adoption would give the child a more secure and permanent family structure.

Contact a DuPage County, IL Paternity Lawyer

If you question whether you are the biological father of your presumed child, you need an experienced attorney to guide you through your legal options. A Naperville, IL family law attorney at Calabrese Associates, P.C. can establish paternity and negotiate your responsibilities as a parent. To schedule an appointment, call 630-393-3111.