Behold the 1st celebrity commandment: Thou shalt not do the dirty on your family - for they are the ones that know the real juicy stuff. This cardinal rule was broken by Madonna. She reportedly dumped her brother, Christopher, once she started dating Guy Richie. According to The New York Post: "Her brother Christopher Ciccone, who had a falling-out with Her Madgesty several years ago, has collaborated with British journo Wendy Leigh on an expose of his sister for Simon Spotlight Entertainment, an imprint of Simon and Schuster - and it's going to be 'brutal.'  'It's extremely graphic and devastating,' said a source who declined to give details. 'He wrote it on the sly without telling Madonna. They want to put it out before her lawyers can get a hold of it.' The book, due out next month, has a massive print run of 350,000.  A dismayed friend of Madonna said, 'We'd heard rumors, but didn't realize he'd actually written it. He was there through the crazy years and has many stories to tell, I'm sure. He's seen it all. Oh, my.' Ciccone - a gay decorator/chef once described by Rupert Everett in Everett's biography as 'a solid raft for Madonna in the shark-infested waters' - was ditched by his sister after she hooked up with her now husband Guy Ritchie, who Everett said was 'uncomfortable around queens'." And there we thought Madonna couldn't be more exposed...