A group of family members and their real estate trusts are suing Boston-based Mintz, Levin, Cohn, Ferris, Glovsky and Popeo and a former partner at the firm, Steven Rosenthal, for allegedly misusing his position to enrich himself and a friend.

Rosenthal was co-managing partner of Mintz Levin when he left two years ago to become chief executive officer of privately held real estate investment and development company Northland Investment Corp.