Denise Richards has been raising Brooke Mueller's kids for over a year.

The 42-year-old actress was granted temporary legal guardian for her ex-husband Charlie Sheen and Brooke's twin sons, Bob and Max, when child protective services removed them from the socialite's home last month.

However, it has now emerged Denise - who has two daughters, Lola, eight, and Sam, nine, with Charlie - has actually spent far more time with the four-year-old boys than Brooke herself over the last nine months, due to her struggles with drug addiction.

A source told ''Initially, Brooke willingly placed the boys in Denise's care because she was going in and out of rehab, and using drugs. Child protective services has now asked Denise to give specific dates that she had been taking care of the twins, in advance of a big custody hearing in July. The boys have spent more time with Denise than with their own biological mother for the last nine months. The boys are a part of Denise's family, and they are extremely happy in her care.''

Brooke - who is currently being treated at the Betty Ford Clinic in California - is said to be worried she is going to lose the $55,000-a-month child support fees she receives from 'Anger Management' star Charlie.

The insider added: ''Brooke doesn't have any money saved and lives month-to-month on the child support. There is no way Brooke is going to get custody back of the twins any time soon.''

The case is set to go to court in July, where social workers are allegedly going to say Brooke should only be granted supervised visitation after leaving rehab as well as being forced to undertake weekly random drug tests.

Denise also has an adopted daughter, 23-month-old Eloise.