Kevin Federline Uncovers the 'Drunk' Phone Call That Was the 'Final Straw' in Britney Spears Marriage

Britney Spears' drunken behavior was the "final straw" for Kevin Federline during their marriage.

In his memoir, You Thought You Knew, the 47-year-old detailed the partying that prevented the pop star, now 43, from taking care of their family.

One night in particular — when Spears was out with Paris Hilton and Lindsay Lohan — prompted Federline to end their union.

"I was in Miami for work, trying to stay focused on my commitments, and I got a call," he explained. "It was her, Paris Hilton, and Lindsay Lohan on the line, drunk as h---, begging me to come over. I could hear [our kids] Preston and Jayden crying in the background. It had to be three or four in the morning. That call was the final straw."

The former backup dancer had already seen photos in the media of the ladies up all night partying at Paris' home in Malibu.

"But hearing my kids crying while she was doing God-knows-what? That was it. Any deep-seated sliver of hope that I’d held onto, that we might still somehow pull it together for the kids, died right then," he asserted.

Kevin believed Britney "wasn't ready to change," and he "couldn’t keep waiting for her to figure it out."

The exes were married for two years before finalizing their divorce in July 2007. They share sons Sean Preston, 20, and Jayden James, 19.

In You Thought You Knew, the dad also disclosed more of Britney's concerning behavior toward the kids. He alleged that the singer punched their eldest son in the face and was so obsessed with their youngest, she bathed with him until he was 10 or 11.

"It was clear he was uncomfortable, to put it mildly, and I had to step in and make it stop," he wrote.

Kevin claimed Britney babied Jayden and favored him over their firstborn.

"This had gone on his whole life at that point, just one more thing that required my intervention to stop. It was a pattern: she’d pull him into her room at all hours, leaving Preston alone," the actor explained. "The imbalance in her attention towards them was beyond frustrating — it was harmful."

Kevin also alleged that the "Toxic" singer would hover over her children with a knife in her hand as they slept.

"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 confessed. "Then she’d turn around and pad off without explanation."