Mass. Gen. Laws ch. 217 § 2
There shall be six judges of probate in the county of Middlesex, four judges of probate in the counties of Norfolk, Bristol, Suffolk, Worcester and Plymouth, three judges of probate in each of the counties of Essex and Hampden, and two judges of probate in the county of Barnstable. The chief justice of the probate and family court department shall designate one justice to be the first justice of a particular court; provided that appropriate consideration shall be given to seniority, length of service in that particular court and managerial ability. Said first justice shall have the powers enumerated in section ten A of chapter two hundred and eleven B and shall be the administrative head of that particular court and shall have authority over all personnel employed therein; provided, however, that registers shall have responsibility for the internal administration of their respective offices, including personnel, staff services and record keeping. A first justice or a register of the court may submit any dispute that arises between said first justice and said register concerning the management and administration of the office of the register, the duties, powers and obligations of the register, or a member of their staff, or the interpretation of the personnel standards provided for under section eight of chapter two hundred and eleven B, to the chief justice of the department. Any person aggrieved by a decision of a chief justice under this paragraph may appeal said decision to the chief justice of the trial court, who shall, within thirty days, hear and determine the matter.
Each first justice so appointed shall serve as first justice of that court for a five-year term and shall be eligible to serve additional five-year terms in that particular court. Any first justice may be removed from his position as first justice by the chief justice of the probate and family court department; provided, however, that any such removal is not for arbitrary or capricious reasons. Any first justice who is removed from his position as first justice by the chief justice of the probate and family court department may appeal the removal to the chief justice of the trial court. The probate court and the court of insolvency for said counties may be held by one or both of the judges, and, when so held, shall have and exercise all the powers and jurisdiction committed to the respective courts. The judges shall so arrange the performance of their duties as to insure a prompt and punctual discharge thereof. The judges may perform each other's duties when necessary or convenient. Simultaneous sessions of the courts in said counties may be held if public convenience requires. Citations, orders of notice and all other processes issued by the register of probate and insolvency, in this chapter called the register, for any of said counties, shall bear teste of the first judge of said court. Deposits or investments made in the name of the judge of probate shall be in the name of the first judge of the court, and shall be subject to the order of the court.
Mass. Gen. Laws ch. 217, § 2