16 Pa. Stat. § 4703
The retirement system shall be under the sole direction of a board, which shall consist of the county chief executive; one member, who shall be a member of the retirement system, appointed by the chief executive with the consent of county council; one member, who shall be a member of the retirement system, appointed by county council; the controller; the treasurer; and two persons elected by ballot from among the members of the retirement system. The terms of such members shall be four years. Ballots shall be mailed to each member of the retirement system at least twenty (20) days prior to the date of the election. A vacancy occurring during the term of any member of the board shall be filled for the unexpired term by the appointment or election of a successor in the same manner as his predecessor. A majority of the members of the board shall constitute a quorum for the transaction of any business.
16 P.S. § 4703