In one of those whowouldathunkit stories, hip hop impresario Kevin Federline has pleaded estranged wife Britney Spears to enter rehab. K-Fed - who was kicked to the curb courtesy of Britney's foot last November - has been trying to convince the paparazzi princess to clean up her life and has even threatened to take their two sons away from her. A source tells Star magazine: "Kevin has tried to convince Britney to check herself into rehab from every possible angle. First he tried threatening to take away the kids, and then he tried pleading with her to take care of herself." K-Fed has even joined forces with Britney's mom Lynne in a last-ditch effort to convince Brit-Brit to be a better mother to her two children, 16-month-old Sean Preston and four-month-old Jayden James. The source adds: "Kevin is afraid that Britney is going to hurt herself. Britney isn't spending enough time with the kids. They are being raised by strangers. He has told Britney to get help before it's too late." My, my, my -- how tables have turned. Not too long ago, K-Fed was the negligent babydaddy with no career and Britney was the embattled mother-of-two just trying to make. Oh what a year can do!