[J.K. Rowling] interviewed by Emma Watson, Feb 1 2014
I wrote the Hermione/Ron relationship as a form of wish fulfillment. That’s how it was conceived, really. 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.

[Emma Watson] I think there are fans out there who know that too and who wonder whether Ron would have really been able to make her happy.