A trust which provides for one or more successor beneficiaries upon the death of the trustor is not invalid, merged or terminated if:
(1) There is a trustor who is the sole trustee and the sole beneficiary during the trustor's lifetime; or
(2) There are two or more trustors, one or more of whom is trustee, and the beneficial interest of the trust is in one or more of the trustors during the lifetime of the trustors.