Sources tell In Touch magazine that Thicke secretly dated the Toxic hitmaker a decade ago (03), months before Spears wed Jason Alexander in Las Vegas in 2004 - and a year before he made childhood sweetheart Patton his wife (05).
An insider tells the publication, "He was trying hard to develop a reputation as a hot, young singer, and Britney was the biggest thing in showbusiness. They started hooking up."
According to the source, the romance began when Thicke and Spears were working on a project that was never released back in 2003, shortly after the pop star split from Justin Timberlake.
Thicke's reps have denied the story.