Kevin Federline wasn't so innocent himself at the start of his relationship with Britney Spears! In his upcoming memoir, You Thought You Knew, per Us Weekly, the 47-year-old looked back on the time that he first met the pop star. It went down in 2004 when K-Fed was a backup dancer for the band LFO, who opened for Britney during her tour four years prior. Her backup dancer, Teresa Espinosa, who "lived in the same quadruplex" as him at the time, introduced them at the Hollywood nightclub Joseph's, and the sparks flew between them instantly.