According to this interview, Hermione no longer has a sister in canon either.
The relevant Q and A:
Does Hermione have any brothers or sisters?
No, she doesn’t. When I first made up Hermione I gave her a younger sister, but she was very hard to work in. The younger sister was not supposed to go to Hogwarts. She was supposed to remain a Muggle. It was a sideline that didn’t work very well and it did not have a big place in the story. I have deliberately kept Hermione’s family in the background. You see so much of Ron’s family so I thought that I would keep Hermione’s family, by contrast, quite ordinary. They are dentists, as you know. They are a bit bemused by their odd daughter but quite proud of her all the same.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapters 91 & 92 . The previous thread has passed 500 comments.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18,19,20.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: