Texas Estates Code - EST § 256.151. General Proof Requirements

(1) the testator is dead;

(2) four years have not elapsed since the date of the testator's death and before the application;

(3) the court has jurisdiction and venue over the estate;

(4) citation has been served and returned in the manner and for the period required by this title; and

(5) the person for whom letters testamentary or of administration are sought is entitled by law to the letters and is not disqualified.