Mont. Code Ann. § 70-29-103

The interests of all the persons in the property, whether such persons be known or unknown, must be set forth in the complaint specifically and particularly, as far as known to the plaintiff; and if one or more of the parties or the share or quantity of interest of any of the parties be unknown to the plaintiff or be uncertain or contingent or the ownership of the inheritance depend upon the executory devise or the remainder be a contingent remainder so that such parties cannot be named, that fact must be set forth in the complaint.