Derek Shepherd is a world-renowned brain surgeon at Seattle Grace Hospital. A transplant from New York, Derek has come to the Pacific Northwest to set his own path after having left his wife Addison Montgomery Shepherd. His lifelong best friend is Dr. Mark Sloan, a plastic surgeon who he left behind in New York after learning that he'd had an affair with Addison. Sloan and Addison both eventually join up with Derek in Seattle. Derek is the only son of a single mother who also had four girls