Britney Spears stopped paying child support to Kevin Federline last year, when their son Jayden turned 18 years old. Britney had been paying child support to K-Fed since 2008, and in that time, K-Fed had gone to court a few times to work out issues in their custodial arrangement and child support. He mostly negotiated with Britney’s father, Jamie Spears. While Britney was in a conservatorship, the custodial arrangement was loose, but Kevin never really “kept” Sean and Jayden away from Britney. When the boys became teenagers, he listened to their concerns about Britney, and he backed up their decision to spend less time with Brit. Well, soon after Jayden’s 18th birthday, Kevin announced that he was writing a book. The NY Times got an excerpt and they also spoke to Kevin.

In a new memoir, Kevin Federline, the dancer, D.J. and ex-husband of Britney Spears, provides his perspective on their strained relationship, and says he is concerned that the decision four years ago to release the pop star from her conservatorship may have been ill-advised.

In “You Thought You Knew,” due Oct. 21, Federline, 47, charts his path from teenage knucklehead growing up in Fresno, Calif., to husband and father of two children with the singer. He and Spears finalized their divorce in 2007 after three years of marriage and then began a prolonged, messy custody battle that ended in 2008. In his book, Federline recounts his version of that dispute and talks of Spears’s use of drugs and alcohol and angry outbursts during the late stages of their marriage.

In the 18 years since their split, Federline has observed his ex-wife largely from a distance as the pair co-parented. “We haven’t spoken in years,” Federline told The New York Times in an interview. But he writes about becoming increasingly concerned with what he describes as Spears’s erratic behavior, which he learned about mostly secondhand from their two sons, Sean Preston, now 20, and Jayden James, 19.

In one chapter, he recounts the time when the boys, as teenagers, declared that they did not want to go back to their mother’s house for several reasons, including fear.

“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,” he writes. “Then she’d turn around and pad off without explanation.”

In the penultimate chapter of the book, Federline fully expresses his concern. “The truth is, this situation with Britney feels like it’s racing toward something irreversible,” he writes. “It’s become impossible to pretend everything’s OK. 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 spokesman for Spears declined to comment on Monday. In her memoir, which is being turned into a film, Spears disputes that she ever had significant substance abuse issues and characterizes her custody battle with Federline as traumatizing. She writes that Federline had not let her see her sons for weeks on end and “tried to convince everyone that I was completely out of control” as part of his bid for full custody years ago.

Federline, who has also dabbled in reality TV, said he had not discussed the contents of the memoir with Spears.

“I’ve never, ever, once, been against Britney,” Federline said in the interview. “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.”

[From The NY Times]

Britney’s rep released a statement to People Mag in response: “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. 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 [The Woman in Me].”

My complicated and unpopular view is that K-Fed was never the villain of the story. He’s done some sleazy things, but from where I sit, he stepped up as a father and became the adult he needed to be when their sons were just babies. Kevin hasn’t centered Britney’s needs and desires… because that’s not his job. His job was being the responsible parent and trying to work within this system to try to help Britney coparent their sons. I think it’s important that Kevin is raising the alarm that all is not well for Britney post-conservatorship. It’s not either/or, in my opinion. I think the conservatorship needed to be lifted too, but it was a mistake to think that once the conservatorship was over, Britney would be fine and she would never need any kind of oversight ever again. Kevin was right to back up his sons’ decision to stop seeing Britney as well. That knife story is chilling.

Photos courtesy of Avalon Red, Backgrid.