Christopher Ciccone's relationship with his older sister, Madonna, was once so close that he described it as "a bit like a marriage."
"I was the last person she spoke to at night before she went to bed," he told ABC's "Good Morning America" today. "I was the first person she saw in the morning."
All that changed after Madonna married Guy Ritchie. Ciccone, who is gay, said Ritchie's homophobia drove him and his sister apart.
And like a spurned spouse or jealous lover, Ciccone is now spilling secrets about his sister in his tell-all memoir, "Life with My Sister Madonna," which hit bookstores today.
"It's basic envy," psychoanalyst and family therapist Bethany Marshall told ABCNews.com about why Ciccone's has written a book about his famous sister. "When we feel envious, we want to destroy the object of our envy and bring them down, so we don't have that reminder that we are missing out on something we want."
What's missing besides the closeness he once shared with his sister is the income Ciccone once earned over two decades as a designer, choreographer, director and yes man for Madonna.
"If he was on the Madonna gravy train and she cut him off, he could feel like he's going to get his no matter what, one way or the other," Marshall said. "When people operate at primitive levels and get their feelings hurt or nose out of joint, they always want the other person to pay for making them feel neglected or like a failure."
Ciccone, 47, insisted to "GMA" that he did not write the book to get back at the pop superstar. "I'm not taking revenge at all,'' he said. "I'm telling what I consider to be a great tale."
But Sara Nelson, editor of Publisher's Weekly, has no doubt that Ciccone was paid well by his publisher, Simon Spotlight Entertainment, a subsidiary of Simon and Schuster. "At least half a million, I would think," she said.
The larger the advance, the more the publisher is counting on the book selling.
"Celebrity books, when done right are sure sellers," Nelson told ABCNews.com. "There have been a lot of books about Madonna, just like books about Princess Diana. If they have the right characteristics, they can do very well. Andrew Morton had a certain inside track with Diana. This is Madonna's brother -- somebody who knows her."
Albert Lee, a senior editor at US Weekly, has seen these celebrity tell-all books, like Nancy Anniston's 1999 "From Mother and Daughter to Friends: A Memoir" about daughter Jennifer, come and go, usually after a relative is cut off financially or emotionally from his or her famous family member who is the family breadwinner.
"Some kind of estrangement happens," "Lee told ABCNews.com, "and the sibling or parents gets offered an insane amount of money [by a publisher]. They come out with a book, and the celebrity's publicist releases a statement saying they are disappointed, it's all lies."
But Lee believes readers of Ciccone's book can expect some new revelations about Madonna.
"Who better than a family member to give real insight into what celebrities are like," Lee said. "Christopher and Madonna were superclose, incredibly close for a very long time. It's almost surprising in this day and age that [this book] didn't happen sooner."