Okla. Stat. tit. 60, § 60-34: Contingent remainder in fee, on prior remainder

A contingent remainder in fee may be created on a prior

remainder in fee, to take effect in the event that the persons to

whom the first remainder is limited die under the age of twenty-one

(21) years, or upon any other contingency by which the estate of

such persons may be determined before they attain majority.