A guardian of the property or an executor or administrator of the estate of a minor, incompetent, or deceased beneficiary may, if the fiduciary deems it to be in the best interest of those concerned with the estate of the beneficiary and of those who will take the beneficiary's interest by virtue of the disclaimer and is not detrimental to the best interest of the beneficiary, with or without an order of the court having jurisdiction, shall execute and file a disclaimer on behalf of the beneficiary within the time and in the manner in which the beneficiary himself or herself could disclaim if he or she were living, of legal age, or competent.