Okla. Stat. tit. 84 § 251
The District Court having jurisdiction to settle the estate of any deceased person is hereby granted original jurisdiction to hear and determine the question of fact as to the heirship of such person, and a determination of such fact by said court shall be conclusive evidence of said question in all the courts of this state. Provided, that appeals may be taken from said district court within the time and in the manner provided by law as in other probate matters. If no appeal is taken the judgment of the district court shall be final, and in all cases appealed from the district court when a final determination thereof is had, same shall be a final determination of such fact of heirship. Provided, that where the time limited by the law of this state for the institution of administration proceedings has elapsed without their institution, as well as in cases where there exists no lawful ground for the institution of administration proceedings in said court, a petition may be filed therein having for its object a determination of such heirship and the case shall proceed in all respects as if administration proceedings upon other proper grounds had been regularly begun, but this provision shall not be construed to reopen the question of the determination of an heirship already ascertained by competent legal authority under existing laws.
Okla. Stat. tit. 84, § 251