After almost thirteen years of marriage, Gwen Stefani and Gavin Rossdale filed for divorce on Monday. TMZ reports Gwen "believed he had been unfaithful."

The 45-year-old singer claimed that the 49-year-old Bush frontman was "cheating" on her, with sources telling TMZ that their split was "a long time coming".

Citing "irreconcilable differences" as the cause of separation, Stefani and Rossdale filed divorce papers in a California court dated August 3, seeking joint custody for their kids, 9-year-old Kingston, 6-year-old Zuma, and 17-month-old Apollo.

"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," the ex-couple announced in a joint statement.

Gwen and Gavin started dating in 1995, after meeting at a Bush concert where Gwen's band, No Doubt opened for the show.

The rock stars tied the knot on September 14, 2002 at London's Covent Garden, which was followed by another ceremony in Los Angeles two weeks after.

TMZ added that Gwen also wasn't happy about Gavin spending too much time on the road, pressuring him to fix his schedule to make time for their kids. Gavin reportedly argued Gwen's hypocrisy, telling her she's always busy with her career too.

"If I look back on the whole thing the one thing that's been constant is that we both want the same thing," Gwen told Today show back in January. "'We both want to be married. We both want to be good parents, and so I feel really proud of what we've done together and that we don't... You're gonna get me crying, no don't, I'm going to get all emotional! But I am really proud of it."

Gavin also gushed about Gwen on his interview with Rolling Stone at the same month saying she's taught him on "how to be a better person."