Gwen Stefani and Gavin Rossdale's divorce has turned upside down. According to a new report, the amicable break up is turning out nasty as Rossdale is reportedly demanding a multi-million fortune from his estranged wife.

Radar Online reported that Gavin is now demanding 50 percent of his wife's multi-million dollar fortune as he claims that he was the one who raised their three sons while Gwen was so busy taking care of her career.

"Gavin is now demanding more than half of her fortune," a source told Radar. "He has complained that while Gwen was launching her successful clothing line, continuing her music career, and expanding her brand by appearing as a judge on The Voice, he stayed home with their sons."

The estranged couple who married back in September 2002, reportedly didn't have a prenuptial agreement. That's why Gavin wants to take advantage of it.

The source also claimed that Gavin is currently threatening Gwen to take the matter in court if she won't give him half of her money. He is also asking for a child and spousal support.

"Gwen is furious because at the outset of the divorce, Gavin said he wouldn't go after her money," the source continued. "She is just kicking herself for not getting a prenup."

The source added, "Gwen isn't just going to hand over a huge check to Gavin...She has worked very hard for her money and won't go down without a fight!"

Gwen Stefani's current net worth stands at $80 million, compared to Rossdale's who stands at $35 million.

It's still unclear what led the couple to file for divorce. But their legal documents cited 'irreconcilable differences' as the reason for the split.

"While the two of us have come to the mutual decision that we will no longer be partners in marriage, we remain partners in parenthood and are committed to jointly raising our three sons in a happy and healthy environment," Gwen and Gavin said while announcing their divorce.