740 ILCS 57/45: Joinder of parties.

(a) Two or more persons may join in one action under this Act as plaintiffs if their respective actions have at least one place of illegal drug activity in common and if any portion of the period of illegal drug use overlaps with the period of illegal drug use for every other plaintiff.

(b) Two or more persons may be joined in one action under this Act as defendants if those persons are liable to at least one plaintiff.

(c) A plaintiff need not be interested in obtaining and a defendant need not be interested in defending against all the relief demanded. Judgement may be given for one or more plaintiffs according to their respective rights to relief and against one or more defendants according to their respective liabilities.