Okla. Stat. tit. 84 § 26
Unless the person by whom the interest was created or from whom it would have been received has otherwise provided by will or other appropriate instrument with reference to the possibility of a disclaimer by the beneficiary, the interest disclaimed shall descend, be distributed or otherwise be disposed of in the same manner as if the disclaimant had died immediately preceding the death or other event which causes him to become finally ascertained as a beneficiary and his interest to become indefeasibly fixed both in quality and quantity, and, in any case, the disclaimer shall relate for all purposes to such date, whether filed before or after such death or other event. However, one disclaiming an interest in a nonresiduary gift, devise or bequest shall not be excluded, unless his disclaimer so provides, from sharing in a gift, devise or bequest of the residue even though, through lapse, such residue includes the assets disclaimed. An interest of any nature in or to the estate of an intestate may be declined, refused or disclaimed as herein provided without ever vesting in the disclaimant.
Okla. Stat. tit. 84, § 26