K-Fed's brother claims it is actually he who fathered Britney's seven-year-old son Sean Preston, one of the two children Britney had with Kevin (the other being six-year-old Jayden James).
"C-Fed" has made the explosive allegations in court papers obtained by Radar Online.
"She is out of control and a maniac," Christopher said in the papers.
"I do confess I slept with Britney, and I am the true father, but the public does not need to know."
Whoa! Those are some pretty huge allegations to make. Last week, Christopher filed for a restraining order against Britney, claiming that she had "stolen from, blackmailed and harassed him", according to a National Enquirer report.
Christopher alleged that Britney had stolen his credit card when he recently picked up Britney's kids from Kevin's house.
"Britney ... laughed at me [and] told me my brother Kevin ruined her life. Britney made fun of me and told me I have a small penis," Christopher said in the documents.
"She also blackmailed me and told me if I tell the police that she stole my credit card, that she will tell the world I’m the true father of Sean Preston, not Kevin."
Christopher claimed that he didn't want this to go public, as he felt his "fling" with Britney was "a mistake".
"He says he always felt bad about it and kept it to himself because he didn't want Alisha, his wife at the time, to find out," a Radar insider says.
Britney's ex-husband K-Fed has sole custody of their two children, while Britney has visitation rights several times a week.
According to an US OK Magazine source, Britney is looking to having a baby with fiancé Jason Trawick, who she plans to marry in 2013.