Federline has teamed up with, Britney’s mom Lynne, who arrived at K-Fed’s Tarzana home early Friday morning around the same time as Kevin's mom.

Federline is anxious about his wife's condition - and about the couple's two sons.

Britney's dad, meanwhile, publicly commented on the pop princess' recent troubles, saying his daughter is "a sick little girl." Jamie Spears told Fox News, "We're just trying to take care of her." He also said that Britney's problems are "not about what other people think."

Kevin Federline visited his estranged wife, Britney Spears, in rehab on Friday, PEOPLE has learned.

Spears, 25, is currently being treated at Promises in Malibu. A source familiar with the situation says Federline, 28, has been involved in her stay there. "He cares a lot about her," the source said.

Federline stopped by the facility on Friday and stayed about an hour and a half reports People Magazine.

"Britney scared everyone pretty bad. Kevin is worried that's for sure," a source close to Federline tells PEOPLE. "Kevin just wants her to be OK. He loves her, so however she can get better is just what we'll have to accept. [They] will make it work with the kids – it's all still for them."