In Illinois, achieving legal recognition as a child's parent is integral to retaining any parental responsibilities and privileges beyond visitation. As of 2016, the law no longer distributes custody and visitation in the traditional sense. Instead, parents allocate parental responsibilities, whereas non-parents can achieve only visitation rights.
The state recognizes parentage for individuals married to a birth mother when the child is born, or if the child is born within 300 days of the marriage's dissolution. Similarly, if an individual is in a marriage or civil union with the birth mother, such as the first two instances, and that marriage is declared unlawful or invalid, the individual is still considered the parent of the child for legal reasons. Finally, if an individual marries the birth mother after the child is born and agrees to have his or her name placed on the child's birth certificate, this is a viable path to parentage.
For men in same-sex marriages, legal adoption seems to be the most viable way to achieve legal parentage for a child. If two men marry and one of them has a biological child, the law does not yet have the mechanisms to offer the father's spouse parentage as it does to a birth mother's spouse. All of the four recognized paths to parentage outlined above apply to someone entering a legal union with the birth mother, and do not extend to spouses and partners of biological fathers.
Parental rights are always emotional things to grapple. If you believe that you should have parental rights to a child you love, it is wise to enlist the guidance of an experienced family law attorney who can help you examine the law and understand how best to fight for a role in the life of the child.
Source: The News Gazette, "How does custody work in gay marriages?," John Roska, May 14, 2017