Sounds like a disgusting place, and the parents should be ashamed of themselves, but unless the kids are being physically abused or their health is being compromised it's better for them to stay with their parents.
It's incredibly traumatic for kids to be separated from their parents and it's almost inevitable that kids who spend any extended period of time in the foster care system end up damaged long term by the experience.
Kudos for helping
. The best thing you could do for the kids is to try to help the parents turn things around.