Section 750 ILCS 5/212 - Prohibited Marriages(a) The following marriages are prohibited: (1) a marriage entered into prior to the dissolution of an earlier marriage, civil union, or substantially similar legal relationship of one of the parties, unless the parties to the marriage are the same as the parties to a civil union and are seeking to convert their civil union to a marriage pursuant to Section 65 of the Illinois Religious Freedom Protection and Civil Union Act;(2) a marriage between an ancestor and a descendant or between siblings , whether the relationship is by the half or the whole blood or by adoption;(3) a marriage between an uncle and a niece, between an uncle and a nephew, between an aunt and a nephew, or between an aunt and a niece, whether the relationship is by the half or the whole blood;(4) a marriage between cousins of the first degree; however, a marriage between first cousins is not prohibited if: (i) both parties are 50 years of age or older; or (ii) either party, at the time of application for a marriage license, presents for filing with the county clerk of the county in which the marriage is to be solemnized, a certificate signed by a licensed physician stating that the party to the proposed marriage is permanently and irreversibly sterile;(b) Parties to a marriage prohibited under subsection (a) of this Section who cohabit after removal of the impediment are lawfully married as of the date of the removal of the impediment.(c) Children born or adopted of a prohibited or common law marriage are the lawful children of the parties.Amended by P.A. 098-0597,§ 905, eff. 6/1/2014.Amended by P.A. 094-0229, § 15, eff. 1/1/2006.P.A. 89-459, eff. 5-24-96.