I read somewhere that at one point JK Rowling had planned to pair Fred Weasley with Hermione Granger, but then changed her mind. Supposedly, she said this in an interview. However, I can't find any citations for this. Is there any evidence or is this just an urban myth?
I've managed to trace the genesis of the 'Fred and Hermione' rumour down to a posting on the 'HP Facts' Pinterest site. Fact #209 has been reposted approximately 20,000 times on Pinterest and many more times on Twitter and Facebook. It appears to be merely a fan-theory, like many of the other spurious "facts" on the now defunct website.
In recent days, Rowling has mentioned that she seriously considered pairing Hermione with Harry (e.g. rather than Ron) but I've not read anywhere that she seriously considered pairing Hermione with any other character.
Okay in The interview with JK Rowling, she said that MAYBE Harry and Hermione would have made the better pair, she and Emma Watson were talking of the Harry and Hermione romance as hypothetical discussion. And yes JK Rowling did say Ron and Hermione would most likely need couple counseling, however that they would turn out fine (again in a jesting tone). JK Rowling also said that Ron and Hermione need each other to balance the other out, she to make him less insecure, and her to be less uptight and critical. And to answer your question about Fred and Hermione I read in an interview that she had always intended to pair Hermione with Ron, and that she had always intended to have Fred die at some point, however we can always ship. And believe me guys Fred and Hermione are my all time favorite ship in the series. :)
According to J.K. Rowling in early interviews, Fred Weasley was going to live while Arthur was going to die in Order of the Pheonix and Ron was going to be killed out of "sheer spite". She admitted that if this plan was to be put in order Fred Weasley and Hermione Granger would have ended up in a relationship. Because this is not what happened, she admitted she regrets the Ron and Hermione pairing, after "stepping back" from the series, and prefers the Harry and Hermione pairing. She even claimed she could see Ron and Hermione needing large amounts of marriage counseling. This is what she has most recently said about relationships in the series and she has not mentioned the Fred and Hermione pairing further.