Mass. Gen. Laws ch. 190B § 3-410
If 2 or more instruments are offered for probate before a final order is entered in a formal testacy proceeding, more than 1 instrument may be probated if neither expressly revokes the other or contains provisions which work a total revocation by implication. If more than 1 instrument is probated, the order shall indicate what provisions control in respect to the nomination of an executor, if any. The order may, but need not, indicate how any provisions of a particular instrument are affected by the other instrument. After a final order in a formal testacy proceeding has been entered, no petition for probate of any other instrument of the decedent may be entertained, except incident to a petition to vacate a previous probate order and subject to the time limits of section 3-412.
Mass. Gen. Laws ch. 190B, § 3-410