<P> Lexie Grey is the daughter of Thatcher Grey (Jeff Perry) and his second wife, Susan Grey (Mare Winningham). She grew up with her younger sister, Molly Grey - Thompson (Mandy Siegfried) and throughout her childhood was kept unaware that she also had an older half - sister, Meredith Grey (Ellen Pompeo), born to Thatcher and his first wife, Ellis Grey (Kate Burton). Lexie is first mentioned when Molly is admitted to Seattle Grace Hospital, with Molly informing Meredith that Lexie is a student at Harvard Medical School . At some subsequent point, Lexie learns of Meredith's existence . She graduates from medical school and is accepted to take her surgical internship at Mass General hospital, but following her mother's sudden death from complications stemming from the hiccups, Lexie instead opts to move back to Seattle to be closer to her father, taking up an internship at Seattle Grace Hospital, one year behind Meredith who is due to begin her residency . </P> <P> Lexie has an eidetic memory, which is often used as a valuable resource and earns Lexie the nickname "Lexipedia ." </P> <P> In contrast to Meredith, Lexie came from a loving home with a happy upbringing . Meredith once said of her: "She was raised right . With parents and rules and smiley face posters on her wall ." Her idealistic upbringing leaves her unprepared to deal with the many hardships she faces during the course of the show, and she often has difficulties understanding and accepting the darker side of human emotions . Despite this, Meredith and Lexie form a wonderful familial bond with Lexie eventually moving into Meredith's house . </P> <P> Lexie is incredibly sympathetic and empathetic often becoming very emotionally invested in her patients and their families . She uses her photographic memory often to help the other surgeons as well as herself . She has a high aptitude for both plastics and neurosurgery and is generally seen as one of the better young surgeons at the hospital often being asked to assist on many of the higher profile surgeries . </P>

When do lexie and sloan first get together