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Kevin Federline writes in his new memoir that his sons claimed their mom Britney Spears would sometimes stand in at their bedroom doorway holding a knife while watching them sleep

The pair share sons Sean Preston, 20, and Jayden James, 19

Federline's memoir You Thought You Knew is out Oct. 21

Britney Spears ’ sons claim that the pop star would watch them as they slept with a knife in her hand, according to their dad Kevin Federline ’s bombshell new memoir .

Federline, 47, relays the knife incident — which he says happened more than once — in his new memoir You Thought You Knew , which has been excerpted by The New York Times .

“They would awaken sometimes at night to find her standing silently in the doorway, watching them sleep — ’Oh, you’re awake?’ — with

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