Tex. Civil Practice and Remedies Code § 37.005

A person interested as or through an executor or administrator, including an independent executor or administrator, a trustee, guardian, 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, mentally incapacitated person, or insolvent may have a declaration of rights or legal relations in respect to the trust or estate:

(1) to ascertain any class of creditors, devisees, legatees, heirs, next of kin, or others;

(2) to direct the executors, administrators, or trustees to do or abstain from doing any particular act in their fiduciary capacity;

(3) to determine any question arising in the administration of the trust or estate, including questions of construction of wills and other writings; or

(4) to determine rights or legal relations of an independent executor or independent administrator regarding fiduciary fees and the settling of accounts.