Ciccone and Madonna were close when she first launched her career
Madonna's brother Christopher Ciccone has revealed in his memoirs that the star is "passionately committed" to her marriage with director Guy Ritchie.
Madonna's representative Liz Rosenberg said the star had not read the memoir but found it "very upsetting" that Ciccone was selling a book about her.
The book, Life With My Sister Madonna, is due to come out on Tuesday, but was previewed by the Associated Press.
It hits the bookshelves amid reports the singer's marriage is in trouble.
Further speculation has linked the 49-year-old to the break-up of baseball player Alex Rodriguez's marriage.
The 32-year-old, who plays for the New York Yankees, was reported to have made late-night visits to the singer's New York apartment.
His wife, Cynthia, filed for divorce on Monday.
But Madonna issued a statement saying that she has "nothing to do with the state of his marriage or what spiritual path he may choose to study".
On Wednesday Ms Rosenberg told the Reuters news agency Madonna's marriage "does not need saving".
She also denied reports the star is dating Rodriguez.
Ciccone has included gossip about Madonna's sex life in the book and stories about various stars, including Sean Penn, Bruce Willis and Gwyneth Paltrow.
The singer, known for hits such as Like A Virgin and Holiday, first worked with her younger brother at the start of her career.
Reports claim Madonna and Ritchie's eight-year relationship is on the rocks
He also designed and directed her Girlie Show tour in 1993 and served as artistic director of her 1991 documentary, Madonna: Truth or Dare.
But in his book he says they are no longer close and blames Ritchie for "the death knell" of their close bond.
Ms Rosenberg agreed that the sibling relationship was barely in existence now.
"I would have to assume she has come to terms with the fact that they do not have a close and loving relationship.
"And with the book coming out, I assume that will remove the chances of that ever happening," she said.
Earlier this year, shops were asked to order the book without knowing the author or subject.
Last month, the publisher released the subject matter and who it was by.