Any of the relief specified in this article may be sought by bill in equity filed by a fiduciary, as defined in this article, or by any other person having an interest in the subject matter of the proceedings. A person under a disability, fiduciary, all those who would be the heirs or distributees of the defendant person under disability if he had died at the time of the commencement of this proceeding, except as provided in § 8.01-78, and all other persons interested in the subject matter of the proceeding, shall be made parties defendant when not parties plaintiff.