What does Kevin Federline’s next book say about Britney Spears?

The ex-husband of pop star Britney Spears is giving new details about the couple’s strained relationship in his new memoir You Thought You Knew.

Kevin Federline, her former backing dancer, presents a picture of Spears’ allegedly erratic behavior as a wife and mother, and says he continues to worry about her well-being.

Spears has spoken out against the book, which will be published Tuesday, and accuses Federline of trying to profit from his association with her.

Federline makes a number of allegations against Spears, in memoirs shared with the BBC ahead of the book’s release by publisher Listenin.

He accuses Spears of unhealthy behavior as a mother, including drinking when she was pregnant and taking cocaine while her two sons were still breastfeeding. Spears has previously denied having substance abuse problems.

When they were teenagers, the couple’s sons were afraid of Spears, Federline also claims. “They would sometimes wake up in the night to find her standing silently in the doorway, watching them sleep – ‘Oh, are you awake?’ – with a knife in his hand,” he wrote. “Then she would turn around and walk away without explanation.”

Federline also expresses concern for his ex-wife, writing, “The truth is, this situation with Britney feels like it’s heading toward something irreversible. From where I sit, time is running out and we are closing in on the 11th hour.”

He writes that he favored a conservatorship, under which many aspects of Spears’ life were controlled by others for years. Of the Free Britney movement, Federline writes that he could “never fully support it.”

The couple reunited in the summer of 2004, after Spears’ commercial peak.

They married a few months later and quickly welcomed their two sons: Preston, now 20, and Jayden, now 19.

Spears filed for divorce in 2006 and the divorce was finalized in 2007.

The couple publicly fought for custody of their sons, and Federline eventually won sole custody of the boys.

Following receiving full custody of Federline, Spears was seen behaving in a manner that Federline describes in his book as irregular.

She made headlines with incidents like shaving her head and hitting a photographer’s car with an umbrella.

These public incidents raised concerns about her mental well-being, and after she was taken to the hospital twice, a temporary guardianship was established in 2008 and made permanent later that year.

Spears remained under this controversial arrangement until 2021, under which her father and others controlled her finances and aspects of her personal life. She only regained custody of her children after it was lifted.

Spears accused Federline of attacking her during her recent press appearances to promote the book. She described the content of the memoir as “extremely hurtful and exhausting”, but suggested that the work would sell better than her own memoir.

In that book, The Woman in Me, Spears accused her ex-husband of trying to “convince everyone that I was completely out of control.”

Spears also defended her relationship with her sons. “I have always pleaded and screamed to live with my boys,” she wrote on social media on October 15, adding that “relationships with teenagers are complex.”

In a statement to US media, a spokesperson for Spears added: “With the news of Kevin’s book being released, once again he and others are taking advantage of her and unfortunately this comes after child support for Kevin ended. All she cares about is her children, Sean Preston and Jayden James, and their well-being during this sensationalism. She has detailed her journey in her memoir.”

The BBC has contacted Federline’s lawyer for comment on Spears’ counter-accusations.

While the couple made headlines during their relationship and subsequent divorce, Federline in particular has largely stayed out of the spotlight in recent years. And recently, the spotlight on Spears has largely been on her social media posts.

Federline said he had been thinking about writing a book for many years, but wanted to wait until his children were older to finish it.

“I took it up and tabled it several times over a period of probably five years,” he told the Associated Press. “I think it’s a very good description of me, of who I am, of the father that I have become, of the husband that I am, of the ex-husband that I am.”

He also told AP: “I want my children to be able to move forward with their lives and know that the truth about everything is out there.”