In an interview with Wonderland Magazine JK Rowling says that she screwed up at least a portion of the Harry Potter books.
“For reasons that have very little to do with literature and far more to do with me clinging to the plot as I first imagined it, Hermione ended up with Ron. I know, I'm sorry, I can hear the rage and fury it might cause some fans, but if I'm absolutely honest, distance has given me perspective on that. It was a choice I made for very personal reasons, not for reasons of credibility. Am I breaking people's hearts by saying this? I hope not.”
She goes on to say that if she had to do it over again Harry would have ended up with Hermione and the way it stands now Hermione and Ron definitely would need marriage counseling and probably would get divorced. Do they have divorces in the wizarding world? Does anyone remember any other couple getting divorced? It was obvious that Harry and Hermione belonged together but I don't have a huge problem with it. I kind of imagined Ron ending up single and a lot like Lenny from That Thing You Do. You know, moves to Vegas or Reno and becomes a drunk who makes a couple of bucks using magic whenever he needs a boost. It's unreasonable to expect that everyone turned out perfectly when they grew up.