 Later additions to the residency program include Lexie Grey ( Chyler Leigh ) , Meredith 's half @-@ sister . Grey is killed alongside Mark Sloan in the season eight finale ; Leah Murphy ( Tessa Ferrer ) ; Shane Ross ( Gaius Charles ) , who departs alongside Yang in the tenth season finale ; Stephanie Edwards ( Jerrika Hinton ) ; Jo Wilson ( Camilla Luddington ) , a doctor who begins a romantic relationship with Karev ; Andrew Deluca ( Giacomo Gianniotti ) , the love @-@ interest of Meredith 's half sister Maggie Pierce ( Kelly McCreary ) , who also serves as head of cardio ; and Benjamin Warren ( Jason George ) , an anesthesiologist and currently a resident , has to balance his wife Miranda Bailey 's new role as Chief of Surgery with his own desire to succeed . Season twelve sees the arrival of Nathan Riggs ( Martin Henderson ) , while Meredith appointed head of general surgery - a post previously held by her mother . 
