Kevin Federline's brother is claiming he is the biological father of Britney Spears' eldest son, according to the National Enquirer.

The singer was married to backing dancer Kevin from 2004 to 2007.

The former couple had two children, seven-year-old Sean Preston and six-year-old Jayden James.

According to the tabloid, Kevin's brother Christopher has filed court documents claiming he slept with Spears while she was married to his brother.

Christopher apparently filed for a temporary restraining order against Britney in US District Court in Tampa, Florida on December 18.

He claims she stole from him, blackmailed and harassed him. He also delivers the paternity bombshell in the filing, according to the Enquirer.

In one incident, Christopher reportedly claims Spears stole his credit card, made $4,500 in charges and threatened to tell the public he is Sean Preston's biological father if he went to police.

"I do confess I slept with Britney, and I am the true father, but the public does not need to know," he is quoted as saying.

A spokesperson for the star has yet to confirm the report.

Spokespersons for the Federline brothers have not issued comment.

- Cover Media