Tex. Estates Code § 401.003

(a) All of the distributees of a decedent dying intestate may agree on the advisability of having an independent administration and collectively designate in the application for administration of the decedent's estate, or in one or more documents consenting to the application for administration of the decedent's estate, a qualified person, firm, or corporation to serve as independent administrator and request that no other action shall be had in the probate court in relation to the settlement of the decedent's estate other than the return of an inventory, appraisement, and list of claims of the decedent's estate. In such case the probate court shall enter an order granting independent administration and appointing the person, firm, or corporation designated by the distributees as independent administrator, unless the court finds that it would not be in the best interest of the estate to do so.

(b) The court may not appoint an independent administrator to serve in an intestate administration unless and until the parties seeking appointment of the independent administrator have been determined, through a proceeding to declare heirship under Chapter 202, to constitute all of the decedent's heirs.