Whenever the remainder of a lifetime or testamentary trust passes, whether outright or in further trust, to two or more designated beneficiaries, and such remainder is ineffective in part and no effective alternative disposition has been made in the governing instrument, such ineffective part shall pass to the other designated beneficiary or, if there are two or more other designated beneficiaries, to such beneficiaries in the proportions that their respective interests in such principal bear to the aggregate of the interests of such designated beneficiaries in such principal.