Madonna and husband Guy Ritchie separated briefly in 2003 after a series of counselling sessions, according to a British author.
Wendy Leigh - who co-wrote Life With My Sister Madonna with the singer's brother Christopher Ciccone - claims Madonna confessed to the temporary split in a letter to her sibling.
But the revelation about the couple - which has recently been dogged by split rumours - did not feature in the newly-released book, reports Fox News.
Leigh recalls "Madonna had serious reservations" about the marriage, just three years into their marriage and following the birth of their son, Rocco.
She says, "(Madonna) detailed her marriage to Guy in a way that a woman usually doesn't discuss her husband with her brother. It showed a side of her that made her very human.
"But I think that this was so soon in the marriage. She was having grave doubts. But so was he. The separation was initiated by him."
The couple soon reunited and will celebrate its eighth wedding anniversary in December (08).