Any person interested as or through an executor, administrator, trustee, guardian or other fiduciary, creditor, devisee, legatee, heir, next of kin or cestui que trust in the administration of a trust, or of the estate of a decedent, an infant, a person who is legally incompetent or a person who is insolvent may have a declaration of rights or legal relations in respect thereto: [2009, c. 299, Pt. A, §2 (AMD).]