Kevin Federline, the ex-husband of pop star Britney Spears, may take the singer to court after a failed Child support negotiation. He currently receives $20,000 each month, but he believes he is entitled to more. Despite the ongoing talks, Kevin took time to celebrate with his kids for his 40th birthday on March 22nd. According to Us Weekly, a source revealed the details of the negotiations and predicted how far this quarrel could go. Despite the inherent stress of the legal battle, Kevin and the kids were still able to have a fun day together.

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Federline to Spears: 'gimme more'

According to Mark Vincent Kaplan, acting lawyer for Federline, Kevin “flatly rejected it.” He intends to request a yearly income and expense declaration from Britney, including her most recent tax returns.

He intends to come up with a number based on this information, which will most certainly be more than she is giving him now. Federline’s motivations come from Britney’s stint in Las Vegas called “Britney: Piece of Me.”

This show had a four-year run and grossed over $137 million. A recent meeting between Kevin's lawyer and Jamie Spears revealed that Kevin is “tremendously disappointed that the offer was rejected, but is prepared to proceed.” Meanwhile, Federline believes that the $20,000/month payment isn’t enough to “recognize the sacrifices he has made because he has gone above and beyond what most people would do in this situation.”

Celebrating the big 4-0

Kevin Federline celebrated his 40th birthday on Wednesday with Sean Preston (12) and Jayden James (11). His wife, Victoria Price, shared photos on her private Instagram account.

The cake was evidently topped with big "4" and "0" candles Federline blew out himself. She also posted a picture of Federline smiling with the cake on Snapchat, using the caption "Happy Birthday Babe."

Federline is taking the birthday party to Vegas, reports The Blast. He's holding his celebration at the Crazy Horse III in Las Vegas. He'll start the party at 11:30 PM and even perform a DJ set later in the night at 12:30 AM. Federline who is himself a musician, dancer, and actor, is living large this weekend for his birthday. If he's stressed out about his ongoing child support battle, he's certainly not showing it.

A 'toxic' relationship

Britney Spears and Kevin Federline were married in 2004 and divorced just three years later in 2007. They are the parents of two sons, Preston and Jayden who are twelve and eleven respectively. After Britney’s breakdown in 2008, Federline won custody of the kids. Britney was placed under the care of her father, Jamie, as conservator. She's currently seeing a new boyfriend.