Mass. R. Dom. Rel. P. Rule 19
Joinder of Persons Needed for Just Adjudication
(a) Persons to be Joined if Feasible. A person who is subject to service of process shall be joined as a party in the action if (1) in his absence complete relief cannot be accorded among those already parties, or (2) he claims an interest relating to the subject of the action and is so situated that the disposition of the action in his absence may (i) as a practical matter impair or impede his 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 reason of his claimed interest. If he has not been so joined, the court shall order that he be made a party. If he should join as a plaintiff but refuses to do so, he may be made a defendant. Identical to Mass.R.Civ.P. 19(a).
(b) Determination by Court Whenever Joinder Not Feasible. If a person as described in subdivision (a)(1)-(2) hereof cannot be made a party, the court shall determine whether in equity and good conscience the action should proceed among the parties before it, or should be dismissed, the absent person being thus regarded as indispensable. The factors to be considered by the court include: first, to what extent a judgment rendered in the person's absence might be prejudicial to him or those already parties; second, the extent to which, by protective provisions in the judgment, by the shaping of relief, or other measures, the prejudice can be lessened or avoided; third, whether a judgment rendered in the person's absence will be adequate; fourth, whether the plaintiff will have an adequate remedy if the action is dismissed for nonjoinder. Identical to Mass.R.Civ.P. 19(b).
(c) Pleading Reasons for Nonjoinder. A pleading asserting a claim for relief shall state the names, if known to the pleader, of any persons as described in subdivision (a)(1)-(2) hereof who are not joined, and the reasons why they are not joined. Identical to Mass.R.Civ.P. 19(c).