A source told ABCNews.com that Richards is caring for four-year-old Bob and Max.
TMZ first reported that the boys had been removed from Mueller's home by officials from the Los Angeles County Department of Children and Family Services.
A spokeswoman for DCFS told ABCNews.com that the department is legally prohibited from confirming whether Mueller or her children are involved with DCFS.
Reps for Sheen and Mueller did not immediately respond to requests for comment.
It's not the first time Richards has stepped in to help Mueller. When Mueller went to rehab in December 2012, Richards also cared for the boys.
Richards told " Access Hollywood " at the time, "This is not the first time I've had all five, they're Sam and Lola's brothers. It was a full house, lots of love and life. Brooke knows anytime, and Charlie, that any time they need help with the boys, that I'm there."
Richards gave birth to daughters Sam and Lola while married to Sheen from 2002 to 2006 and later adopted daughter Eloise.
Mueller was married to Sheen from 2008 to 2011.