Article continues below advertisementBritney Spears' ex Kevin Federline thinks the pop star is headed down a dark path.In his memoir, You Thought You Knew, the former backup dancer, 47, exposed his concerns over his former wife.Federline - who shares sons Sean Preston, 20, and Jayden James, 19, with Britney - thinks she is destined for disaster.Article continues below advertisementSource: MEGAKevin Federline and Britney Spears were married for three years."The truth is, this situation with Britney feels like it's racing toward something irreversible," he wrote.