Joel Madden has reportedly been "leaning on" Cameron Diaz for support in fighting for Nicole Richie.
The rocker and fashion designer tied the knot in 2010 and they have daughter Harlow and son Sparrow together.
There are rumours of trouble in their marriage at the moment, with Nicole being spotted out without wearing her wedding ring recently. While both appear to be putting on a united front on social media by posting cute photos of one another, it's thought things aren't in good shape.
Joel has apparently been relying on sister-in-law Cameron, whos married to his brother Benji, for help.
"Joel is determined to fight for Nicole. He's been leaning on Cameron, saying he doesn't want to give up on the marriage. He says he'll do whatever he can to prove his devotion to her and their family," an insider told British magazine Closer.
Meanwhile Cameron has apparently been "begging" her pal to not throw what she has with Joel away, even inviting Nicole to stay with her while she thinks things over. The former reality star is said to have been open about her marriage woes with friends, admitting she and her husband have been drifting apart over the last few months.
This could be in part due to Joel's stint as a judge on The Voice Australia, meaning he spends long periods away from home.
In contrast, things appear to be going well for Cameron and Benji, who got hitched at the beginning of this year. The couple are apparently keen to start a family and those close to the blonde beauty are sure it's bound to happen soon.
"Having a baby has been something she's dreamed of since meeting Benji and she's happier than ever," a source added.