Kevin Federline reflects on his past marriage to Britney Spears in his upcoming memoir, You Thought You Knew, and makes some wild claims about his ex. An excerpt from the book published via The New York Times on Tuesday, October 14, alleges that Federline, 47, and Spears' two sons - Sean Preston, now 20, and Jayden James, now 19 - were afraid of staying at their mom's house. "They would awaken sometimes at night to find her standing silently in the doorway, watching them sleep - 'Oh, you're awake?' - with a knife in her hand," Federline writes. "Then she'd turn around and pad off without explanation." Federline and Spears, 43, were married from 2004 to 2007. He recalled one evening in 2008 when Spears was placed under an involuntary psychiatric hold following a standoff that involved their sons. "It was one of the hardest nights of my life," Federline writes in the book. "I felt sick over what she was going through. This was someone I had loved. Someone I had built a life with. The mother of my children." Kevin Federline's New Memoir to Detail 'Ridicule' of Britney Spears Marriage Following their split, Spears' father, Jamie Spears, placed her under a conservatorship after the singer suffered a public breakdown. While the legal arrangement has been terminated since November 2021, Federline still has concern for Britney. "The truth is, this situation with Britney feels like it's racing toward something irreversible," the excerpt reads. "It's become impossible to pretend everything's OK." Jason Merritt/Getty Images Federline adds, "From where I sit, the clock is ticking, and we're getting close to the 11th hour. Something bad is going to happen if things don't change, and my biggest fear is that our sons will be left holding the pieces." A representative for Spears responded to Federline's claims in a statement to Us Weekly on Tuesday. "With news from Kevin's book breaking, once again he and others are profiting off her, and sadly it comes after child support has ended with Kevin," the statement reads. "All she cares about are her kids, Sean Preston and Jayden James, and their well-being during this sensationalism. She detailed her journey in her memoir [2023's The Woman in Me]." In an interview with the newspaper regarding the upcoming book, Federline said his sons are his biggest concern at the moment. "I've never, ever, once, been against Britney," he claimed. "I've only tried to help my sons have an incredible relationship with their mother. And it's hard because when I really reflect on everything that's happened - my kids do not know the woman that I married. And I've spent two decades trying to bridge that gap." Britney Spears' 'Happiest Times' Are With Sons Sean Preston and Jayden Federline also addressed the widespread #FreeBritney movement that ran rampant as Spears was in court attempting to break free from her conservatorship. "All those people who put so much effort into that should now put the same energy into the 'Save Britney' movement," Federline writes in his memoir. "Because this is no longer about freedom. It's about survival." Federline also makes a plea to anyone "who has ever been moved by Britney" to share their concern for the exes' kids. "Now, more than ever, they need your support," the book excerpt reads. "I've been their buffer for years, but now it's bigger than me. It's time to sound the alarm." You Thought You Knew is available in bookstores next Tuesday, October 21.