While his estranged wife Britney Spears was busy checking in and out of rehab, Kevin Federline has been taking steps to get custody of the couple's two children. KFed is due to appear in an LA court tomorrow for an emergency hearing, according to a Superior Court spokesperson, who said, "Our best information is he will be here, she won't. But anything is possible." The reason for the hearing has not been made public, but Federline's lawyer may convince the court that a custody hearing that would end the temporary joint custody granted at the beginning of February is urgently required. A rep for Federline says her client has no comment, but sources say the aspiring rapper called his mom last Wednesday and asked for help in looking after five-month-old Jayden James and 17-month-old Sean Preston. "He is beyond sad," says a friend of Federline. "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." Spears's mom, Lynne is also helping to look after the kids. "Britney's family feels that Kevin has been a blessing and they are very impressed with Kevin taking so much responsibility," says a Spears family insider. "Britney's family found out from the news this morning that Britney had left rehab. Britney has not asked to see the kids because she knows she is not well and she does not want to scare [them]. She has no credit cards or cash. She is basically on the run at the moment." Calls to Spears's agent today were referred to her manager, who in turn referred them to the publicist at Spears's label, Jive Records, who left all inquiries unanswered.