Tenn. Code Ann. § 29-15-105: Joinder of counts and parties

(a) The declaration may contain several counts, and several parties may be named as plaintiffs, jointly in one (1) count and separately in others, but not without the consent of the party in person, or by a duly authorized agent, unless the party in person be tenant in common with the party commencing the suit.

(b) If the name of a person be used as a plaintiff contrary to this provision, the suit shall be dismissed at the cost of the plaintiff, on motion of the defendant and the proof of want of authority.