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, a guardianship, or of the estate of a decedent, an infant, a mental incompetent, or insolvent may have a declaration of rights or equitable or legal relations in respect thereto:
(1) To ascertain any class of creditors, devisees, legatees, heirs, next of kin, or others; or
(2) To direct the executor, administrator, or trustee to refrain from doing any particular act in his or her fiduciary capacity; or
(3) To determine any question arising in the administration of the guardianship, estate, or trust, including questions of construction of wills and other writings.
For the purpose of this section, a “mental incompetent” is one who, because of mental illness, mental retardation, senility, excessive use of drugs or alcohol, or other mental incapacity, is incapable of either managing his or her property or caring for himself or herself, or both.