The Anger Management star has four-year-old twins Bob and Max with his ex-wife Brooke Mueller.
Denise Richards, who divorced Charlie in 2006, had temporarily been looking after the children while their mother visited rehab.
She relinquished custody earlier this year and Brooke's brother Scott took the boys in.
Now RadarOnline reports the twins are in danger of being handed to strangers for the festive period.
Apparently there has been "mystery evidence" concerning Brooke's drug treatment programme, which could affect whether she is granted custody.
“There is a very real possibility that Bob and Max could be placed in foster care because evidence was also uncovered regarding their temporary guardian, Scott, that is riddled with glaring differences in version of events,” a source told the website.
“The [Child Protective Services] department is taking this very seriously, and are considering recommending the boys be placed in foster care, pending the outcome of the investigation.”
Max and Bob were taken out of Denise's care earlier this year due to the boys' reported violent outbursts around her own three children.
“Charlie can’t get custody of the boys, even if he were to have round the clock nannies because of his past behaviour,” the insider explained. “Brooke’s parents won’t be considered. It’s such a sad situation, but the safety and well-being of the boys comes first. Such drastic action wouldn’t be taken unless it was necessary, and sadly, it is.”
The Los Angeles County of Department of Children & Family Services is apparently set to go to court on Thursday based on the alleged new information.