(a) Except as provided by Subsection (b), the settlor of a first trust is considered to be the settlor of a second trust established under this subchapter.
(b) If a settlor of a first trust is not also the settlor of a second trust into which principal of that first trust is distributed, the settlor of the first trust is considered the settlor of the portion of the second trust distributed to the second trust from that first trust under this subchapter.