Unless the decedent or donee of the power has otherwise provided, the property or interest disclaimed devolves (a) as to a present interest, as if the disclaimant had predeceased the decedent or, if the disclaimant is designated to take under a power of appointment exercised by a testamentary instrument, as if the disclaimant had predeceased the donee of the power, and (b) as to a future interest as if the disclaimant had died before the event determining that the taker of the property or interest had become finally ascertained and his interest indefeasibly vested. A disclaimer relates back for all purposes to the date of death of the decedent or the donee of the power.
N.J.S. § 3A:25-45