Continuity mistake: Harry buys the book "One Thousand Magical Herbs and Fungi", but later, the title changes to "One Hundred Magical Herbs and Fungi".
Continuity mistake: While being sorted into houses, Harry looks up at the Sorting Stool, and there are only three people left to be sorted. Professor McGonagall then calls out the names of four more kids.
Answer: Yes. J.K. Rowling was going to give Hermione a younger sister who was a muggle. However, by the time "Harry Potter and the Order of the Phoenix" came out, she felt that it was too late.