765 ILCS 520/3
Minors and persons under legal disability may institute or defend actions by guardian or next friend. Every person, including spouses of owners, having any interest in the right to drill for and remove oil and gas from such lands, whether in possession or otherwise, and who is not a plaintiff, shall be made a defendant to such complaint. Any person claiming or appearing to claim an interest in the right to drill for and remove oil and gas from such land may be made a defendant. When there are or may be any persons interested in the right to drill for and remove oil and gas from such lands whose names are unknown, the complaint shall so state, and such persons may be made parties to such action by the name and description of Unknown Owners.
765 ILCS 520/3