My sister want to take in our nieces siblings

One of my older brothers had a daughter with a woman that is now married and supposed to go to rehab. Her husband is also supposed to be in rehab. So my sister took in my niece and the other kids went with the husband's mom. They where suppose to be in rehab for about a month and then they can get the kids back. Well he just quit rehab and she is going to quit too. But she wants my sister to take her other kids because she can't care for them. I'm just trying to see if that is something that cps will allow? She lives in a trailer and there are 3 rooms. Hers, my nieces, and a empty room. I believe the other kids are 2 girls and a baby. My mom lives across the street and is willing to help out. I personally don't think my sister should. Tho her rent is paid for a while she currently has no job. The kids also don't know us. There will be times when my niece gets to see her dad and I feel bad for how those other kids will feel. We are complete strangers.