By Martin Roberts

TORONTO (Reuters) - J.K. Rowling, whose Harry Potter series made her the first billionaire author, said on Tuesday she was surprised at the fuss surrounding her announcement the boy wizard's head teacher, Albus Dumbledore, was gay.

"It has certainly never been news to me that a brave and brilliant man could love other men," Rowling told a news conference in Toronto, where she is attending an authors' festival.

Rowling, a mother-of-three, made the surprise revelation in New York on Friday, during her first U.S. tour in seven years.

She said Dumbledore was once infatuated with the winsome wizard Gellert Grindelwald, but the two became rivals when Grindelwald turned out to be more interested in the dark than the good arts. Dumbledore went on to destroy Grindelwald.

Reaction has been mainly supportive on fans' Web sites, such as The Leaky Cauldron (www.leakynews.com), where news of Dumbledore's outing has drawn more than 3,000 comments.

Rowling declined to say whether her "outing" of Dumbledore might alienate those who disapprove of homosexuality.

"He is my character. He is what he is and I have the right to say what I say about him," she said.

Rowling said she made no revelations about Dumbledore's sexuality before Friday, because she had never before been asked directly.

"People wanted so much information in advance of the story, that just to keep my sanity and keep my eye on my own plot, I did not give masses away ahead of time," she said.

The seventh and final book in the boy wizard series, "Harry Potter and the Deathly Hallows" became the fastest selling book in history upon its release in July, selling more than 11 million copies in the first 24 hours in Britain and the United States.

The fifth film of the series, "Harry Potter and the Order of the Phoenix", received three nominations on Monday for Britain's film awards, the Baftas.

Rowling said she "probably won't" write a prequel to the series, but did not rule it out.

"Is that (a prequel) not a little bit 'Star Wars Episode I'?" she quipped. "I'm not going to say 'never' because 'never' in my life acts as a red rag to bull and I've immediately wanted to do whatever it is I said never to."

Rowling said she might work on a Potter encyclopedia for charity, but only after a long break.

"It's like the break-up of a marriage. It's a good idea not to see each other for a while, then maybe you can be good friends afterwards," she said.