During seasons 1 to 6 we have heard Derek mention that he has 4 sisters, that's why Mark and Derek became bff's plus Mark stated that Derek's sisters use to have practice sex with Mark. We already met Nancy, there was a mention of Katherine, has there been any hint that we may see or meet the other Shepard sisters maybe have them come to Seattle Grace Mercy West to consult on a case or just to come to Seattle to meet Derek's post-it wife Meredith.

I LOVED the episode when Nancy came and said "everyone has sex with Mark Sloan. It's a rite of passage." It was just one of my favorite one-liners that Grey's is famous for. It's hillarious how she waved off Addison's affair with Mark as a "rite of passage." Well, Addison was married. No ceremonies after the ceremony. Anyway, makes one wonder how many MORE of the sisters were initiated lol.