08/20/2012 04:01

By Bruna Nessif and Katie Rhames

Look at all these exes getting along.

E! News has exclusively learned that Denise Richards got together with her ex-husband Charlie Sheen to throw a birthday party at her Hidden Hills, Calif., home today for—wait for it—Sheen's other ex-wife, Brooke Mueller.

Yep, that happened.

Richards threw a pool party for Mueller's 35th birthday and invited family and friends over (all the kids were there also), however there's no word whether or not Mueller's new man attended.

"Brooke and Denise have spent some time together lately and there is a budding camaraderie there," a source tells E! News, and also shared that all the kids have a good relationship with each other and the girls "are like real big sisters to them."