Federline tells People magazine he vowed to "spend every last dime" to make sure that sons Sean Preston and Jayden James were OK.
"That's all that mattered. I didn't know how much power Britney had. That really scared me," he says.
Federline and Spears split up in 2006 after two years of marriage. The aspiring rapper later gained custody of their boys as Spears' behavior spiraled downward. Spears has said that things fell apart when Federline began focusing on his rap career. But Federline tells the magazine he was more concerned with the children.
"Not that I ignored Britney, but my kids are always most important," he says.