Was Britney Spears a “Toxic” mom? Disturbing new details from her ex-husband Kevin Federline’s scathing new tell-all, “You Thought You Knew,” continue to pour in. In the book, out Oct. 21, he alleges the singer put their now-adult sons, Sean Preston, 20, and Jayden James, 19, through a childhood of trauma. Page Six has the...

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