Texas Civil Practice and Remedies Code - CIV PRAC & REM § 37.005. Declarations Relating to 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.