Texas Estates Code - EST § 202.151. Evidence in Proceeding to Declare Heirship

(a) The court may require that any testimony admitted as evidence in a proceeding to declare heirship be reduced to writing and subscribed and sworn to by the witnesses, respectively.

(b) Except as provided by Subsection (c), in a proceeding to declare heirship, testimony regarding a decedent's heirs and family history must be taken:

(c) If it is shown to the court's satisfaction in a proceeding to declare heirship that, after a diligent search was made, only one disinterested and credible witness can be found who can make the required proof in the proceeding, the testimony of that witness must be taken:

(d) Notwithstanding any other law, a person interested in an estate solely because the person is a creditor or has a claim against the estate may serve as a witness under this section if the person is otherwise a credible witness.