Tenn. R. Civ. P. 19.01
A person who is subject to service of process shall be joined as a party if (1) in the person's absence complete relief cannot be accorded among those already parties, or (2) the person claims an interest relating to the subject of the action and is so situated that the disposition of the action in the person's absence may (i) as a practical matter impair or impede the person's ability to protect that interest, or (ii) leave any of the persons already parties subject to a substantial risk of incurring double, multiple, or otherwise inconsistent obligations by reasons of the claimed interest. If the person has not been so joined, the court shall order that the person be made a party. If the person properly should join as a plaintiff but refuses to do so, he or she may be made a defendant, or in a proper case, an involuntary plaintiff.
Tenn. R. Civ. P. 19.01