As Britney Spears continues to unravel in public, Kevin Federline has been working behind the scenes to take custody of their children away from the erratic pop star.

Kevin , his mother and with the help of Spears' mother Lynne, have joined forces to aid Federline while he has cared for his sons Sean Preston and Jayden James during their mother's recent rehab stints, partying and hotel stays. "He is beyond sad," says a Federline pal. "This is the worst week of his entire life. He doesn't even want to pick up the phone. Things are beyond not well with Britney, and he still loves her."

Federline reportedly is now taking legal steps to protect his children. Kevin has requested an emergency custody hearing Thursday before an L.A. judge (Spears had been granted physical custody of the kids at an earlier hearing). Federline's rep couldn't be reached for comment, but a source confirmed that a custody hearing has been set for Thursday.

K-Fed made a call to his mother, Julie Bleak, on Valentine's Day asking for her to help him take care of the children. Bleak flew to L.A. on Feb. 15 (the same day Spears, 25, checked into the Crossroads Centre rehab facility in Antigua). Our source adds that Lynne Spears has also been present for her grandchildren, taking care of the children round-the-clock with Federline.

"Britney's family feels that Kevin has been a blessing and they are very impressed with Kevin taking so much responsibility,"Source

Labels: Britney Spears, Kevin Federline