Sean Preston Federline was allegedly "terrified" of his mother Britney Spears. And this was when he was just a little boy! Oof. In Kevin Federline's memoir, You Thought You Knew, out this week, the father recalled how his oldest son never wanted to visit with his momma. As Perezcious readers know, after the co-parents' divorce, Kevin won primary physical custody in 2008, the same year Brit was put into her 13-year conservatorship following a string of personal and legal challenges.