Michael Douglas and Catherine Zeta-Jones' marriage is crumbling. The pair, who haven't been spotted together since April 22, have decided to take time apart.

"They're taking a break," one source told PEOPLE Magazine.

Neither star has filed for divorce or moved toward a legal separation, sources added.

The pair, who wed in 2000 at Manhattan's Plaza Hotel, have two children: Dylan, 13, and Carys, 10.

"They want the best for their kids, no matter what happens," a close friend said.

The couple have faced more than their fair share of ups and downs over the last three years – between Douglas's 2010 cancer battle and Zeta-Jones's struggles with bipolar II disorder. The couple officially decided to take time apart after Douglas came back from the Cannes Film Festival in May. Zeta-Jones had recently returned from a scheduled second round of treatment to monitor her bipolar disorder.

“The stress has taken a toll on their marriage,” a friend said.

In May, Douglas expressed his love for Zeta-Jones in Cannes, telling press he was ready to be back home with his wife.

"She comes home tomorrow," he told PEOPLE in May while promoting Behind the Candelabra. "She's doing a really good job of getting balanced. I'm proud of her."