735 ILCS 5/9-113: Joinder of several tenants.

Whenever there is one lease for the whole of certain premises, and the actual possession thereof, at the time of the filing of the action, is divided in severalty among persons with, or other than the lessee, in one or more portions or parcels, separately or severally held or occupied, all or so many of such persons, with the lessee, as the plaintiff may elect, may be joined as defendants in one action, and the recovery against them, with costs, shall be several, according as their actual holdings are judicially determined.