225 ILCS 10/2.04
"Related" means any of the following relationships by blood, marriage, civil union, or adoption: parent, grandparent, great-grandparent, great-uncle, great-aunt, brother, sister, stepgrandparent, stepparent, stepbrother, stepsister, uncle, aunt, nephew, niece, fictive kin as defined in Section 7 of the Children and Family Services Act, or first cousin or second cousin. A person is related to a child as a first cousin or a second cousin if they are both related to the same ancestor as either grandchild or great-grandchild. A child whose parent has executed a consent, a surrender, or a waiver pursuant to Section 10 of the Adoption Act, whose parent has signed a denial of paternity pursuant to Section 12 of the Vital Records Act or Section 12a of the Adoption Act, or whose parent has had his or her parental rights terminated is not a related child to that person, unless (1) the consent is determined to be void or is void pursuant to subsection O of Section 10 of the Adoption Act; or (2) the parent of the child executed a consent to adoption by a specified person or persons pursuant to subsection A-1 of Section 10 of the Adoption Act and a court finds that the consent is void; or (3) the order terminating the parental rights of the parent is vacated by a court of competent jurisdiction.
225 ILCS 10/2.04