[JenB]

Yah, Mary Sue has a brother, but in my old fancircles we called them "male MS"s. It's ok to have an original character in your fanfic, in fact it's a mark of a good writer, but it's not ok to make your character the center of the universe. I believe Mary Sue actually originated in a Trek novel - that's what I've heard but since I've never read the particular story I wouldn't know.

[Bear_in_RoseBear]

I believe Mary Sue actually originated in a Trek novel

From what my wife has told me... there was a female writer of Trek fanfics back-in-the-day (seventies, I think) who placed thinly-veiled versions of herself (always named Mary Sue) into her stories. Said character always wound up saving the ship and having a passionate romance with one of the Big Three (Kirk, Spock, or McCoy). She wasn't the only writer who did this unfortunately, but the term "Mary Sue" eventually grew to include all such fanfiction.