Ginny was the first girl in several generations... there is no older sister
Author's response
Yes and No. When Hogwarts Exposed was started, canon was only up to book four. I used a fanfic, Physhic Serpent, for my fifth and sixth year history. In that fic, Ginny had two sisters who had been kidnapped. Now I wish I had never mentioned them, but I'm not going back and rewrite the entire story to eliminate anything not consitent with canon.