Michael Katsidis' brother found dead

The older brother of Australian lightweight star Michael Katsidis was found dead Tuesday in his Brisbane, Australia, home. Stathi Katsidis, one of the top Thoroughbred horse jockeys in Australia, was 31.

Michael Katsidis, an interim titleholder, is in Thailand training for a Nov. 27 HBO fight in Las Vegas against lightweight champion Juan Manuel Marquez.

Katsidis' manager/trainer Brendon Smith found out about the death in a call from Katsidis' mother and was going to break the news to the fighter.

"We haven't spoken to Michael, but we have spoken to Brendon," David Itskowitch, an executive with Golden Boy, Katsidis' promoter, told ESPN.com. "Our concern right now is for Michael, not as to whether he will fight. He just lost his brother, who he was very close with. However long it takes, he will decide what he will do. Right now the fight is not a concern for us. We're concerned for him."

According to multiple Australian media reports, Stathi Katsidis was found dead by his girlfriend, Melissa Jackson, who also is the mother of their 4-year-old son.

The cause of death has not been determined, although he had a history of drug and alcohol problems, including a positive test for ecstasy in 2008 and a prior drunken driving arrest, according to media reports.

Katsidis was scheduled to ride Saturday.

Dan Rafael covers boxing for ESPN.com. Follow him on Twitter.