It looks like it was the child's mother and her boyfriend that were arrested.
The one friend on the perps myspace is listed as 18 years old. Could be the mother, though, just lying about her age, because she looks a lot like the woman arrested. Hard to tell.
Good question about how many kids are being held like this. As we have seen from other cases, neighbors and family members really need to start being more nosy and to report, and keep reporting if they feel something is wrong. That might limit these kind of case. Unfortunately, it seems that sometimes witnesses who could report and protect the child, end up joining in on the abuse, as we saw with the case of Kyle in CA. Where the heck do such monsters come from? Or, is it that creeps just tend to associate with other creeps?