MFS Investment Management, the Boston-based investment arm of Sun Life Financial, is going with the co-CEO model — announcing that the firm’s president and chief investment officer (CIO), Michael Roberge, has been promoted to share CEO duties with Robert Manning, the firm’s current chairman and CEO since 2004.

The appointment is to take effect on Jan.1, 2015; Roberge will also continue to serve as CIO, although some of his oversight responsibilities will be handed off to two new group CIOs. Kevin Beatty, director of equity, North America, will become CIO global equity, and Bill Adams, director of fixed income will be promoted to CIO global fixed income. They will both report to Roberge.

The firm says that the move will “allow MFS to build out its leadership team and give Manning the opportunity to focus on the firm’s overall strategic direction”. Manning said that, as co-CEO, Roberge “will play a critical role in both guiding our investment team and managing our ongoing global expansion.”

Roberge joined MFS in 1996 and has been a credit analyst, portfolio manager, research director, chief of fixed income, and chief U.S. investment officer, before being promoted to president and CIO in January 2010.