K-Fed Tells HIS SIDE OF THE STORY

Kevin Federline makes shocking claims about his ex-wife, Britney Spears, in a new book — and, despite her pushback, he stands by it

- By Nicholas Hautman / With reporting by Ryan Naumann, Andrea Simpson & Whitney Vasquez

Kevin Federline knows what you're thinking: His new memoir is a cash grab now that his $40,000-a-month child support checks from Britney Spears have run out. "Money's not the root of this thing," Federline, 47, tells Us in an exclusive interview. So, why now? "I've sat back and watched people tell my story through a different lens for 20 years," he explains, noting that his and Spears' two sons, Sean Preston, 20, and Jayden James, 19, are now "old enough to understand it was time for me to tell my story, time for me to finally come forward and put my life in perspective."

You Thought You Knew (out Oct. 21) chronicles how Federline, a former backup dancer for Pink, Destiny's Child