Tex. Estates Code § 1051.104

(a) The person filing an application for guardianship shall send a copy of the application and a notice containing the information required in the citation issued under Section 1051.102 by a qualified delivery method to the following persons, if their whereabouts are known or can be reasonably ascertained:

(1) each adult child of the proposed ward;

(2) each adult sibling of the proposed ward;

(3) the administrator of a nursing home facility or similar facility in which the proposed ward resides;

(4) the operator of a residential facility in which the proposed ward resides;

(5) a person whom the applicant knows to hold a power of attorney signed by the proposed ward;

(6) a person designated to serve as guardian of the proposed ward by a written declaration under Subchapter E, Chapter 1104, if the applicant knows of the existence of the declaration;

(7) a person designated to serve as guardian of the proposed ward in the probated will of the last surviving parent of the proposed ward;

(8) a person designated to serve as guardian of the proposed ward by a written declaration of the proposed ward's last surviving parent, if the declarant is deceased and the applicant knows of the existence of the declaration; and

(9) each adult named in the application as an "other living relative" of the proposed ward within the third degree by consanguinity, as required by Section 1101.001(b)(11) or (13), if the proposed ward's spouse and each of the proposed ward's parents, adult siblings, and adult children are deceased or there is no spouse, parent, adult sibling, or adult child.

(b) The applicant shall file with the court:

(1) a copy of any notice required by Subsection (a) and the return receipts or other proofs of delivery of the notice; and

(2) an affidavit sworn to by the applicant or the applicant's attorney stating:

(A) that the notice was sent as required by Subsection (a); and

(B) the name of each person to whom the notice was sent, if the person's name is not shown on the return receipt or other proof of delivery.

(c) Failure of the applicant to comply with Subsections (a)(2)-(9) does not affect the validity of a guardianship created under this title.

(d) Notice required by Subsection (a) to a relative of the proposed ward described by Subsection (a)(1) or (2) must contain a statement notifying the relative that, if a guardianship is created for the proposed ward, the relative must elect in writing in order to receive notice about the ward under Section 1151.056.