Dumbledore is Gay; not that there’s anything wrong with that.

Apparently when reviewing the script for Harry Potter and the Half Blood Prince J.K. Rowling came across a change from her book that she couldn’t let pass; similar to Kreacher almost getting cut from Order of the Phoenix. The writers added a past love interest for Dumbledore, in flashbacks, and Rowling sent them a note saying you can’t do this revealing the sexual identity of the master wizard. You can read more here.