Cameron Diaz had a sweet reaction to fans discovering she's Nicole Richie's sister-in-law

Fans often forget Cameron Diaz and Nicole Richie are sisters-in-law — each are married to one of the Madden twin brothers (Benji is husband to Diaz, and Joel to Nicole) from the band Good Charlotte — including one particular celebrity watcher, Betches website content director Ashley Fern, who tweeted Monday:

"Nicole Richie & Cameron Diaz are sister in laws and I feel like we don’t talk about that enough," she wrote. The message also got posted up on Betches' Instagram account, and that's where things really took off ... because Diaz commented!

The retired actress wrote a "twin" emoji with "winky faces" and then added, "@nicolerichie." Clearly, this is a relationship that supersedes words.

Diaz and Benji Madden wed in January 2015. They have one child, Raddix, 9 months. Joel Madden, 41, and Richie, 39, who tied the knot in 2010, share Harlow, 12, and Sparrow, 11.

While speaking on her Instagram story in April, as TooFab reported, Diaz noted that she and Richie remain very close. Richie, she said, comes over and watches baby Raddix while Diaz does chores, and both families live near to one another. "It's the best, we're so lucky," Diaz said. "We're so grateful with the fact we can be home here with one another."

And they support one another professionally, as well as personally. Diaz posted a photo of the sisters-in-law embracing at a fashion event for Richie in 2016:

"We're sisters because of our misters and I am SO impressed by and proud of how talented she is," she wrote in part.

We bet Richie feels the same way!