Britney Spears' ex K-Fed will spill everything he knows about popstar once kids turn 18

Britney Spears ex-husband Kevin Federline will reportedly spill all the things he knows about his former wife the moment their children turn 18.

The former backup dancer has decided to write a book on parenting for which he has teamed up with the Hold Me Closer singer’s father Jamie Spears.

Kevin is “writing a book on his experience of fatherhood,” the Journalist Daphne Barak claimed, and the singer's estranged dad has “agreed to help” as per Page Six.

The two men have reconciled their bond and “are now speaking to each other once again” after Kevin obtained a restraining order against Jamie for allegedly abusing his grandson Sean Preston.

Now, an insider spilled to Radar Online that K-Fed "turned down multimillion-dollar book deals" in previous years because he was bound by a legal clause.

"Kevin's divorce settlement and child support payments include a nondisclosure agreement. But that expires when the boys turn 18," the source said of Sean, 17, and Jayden, 16.

"Once that happens, Kevin is free to tell all — and he knows everything,” the insider added.