Mass. Gen. Laws ch. 203E, § 802
Duty of loyalty
(b) Subject to the rights of persons dealing with or assisting the trustee, as provided in section 1012, a sale, encumbrance or other transaction involving the investment or management of trust property entered into by the trustee for the trustee's own personal account or which is otherwise affected by a conflict between the trustee's fiduciary and personal interests shall be voidable by a beneficiary affected by the transaction unless:
(c) A sale, encumbrance or other transaction involving the investment or management of trust property shall be presumed to be affected by a conflict between personal and fiduciary interests if it is entered into by the trustee with:
(g) This section shall not preclude the following transactions, if fair to the beneficiaries: