Should I do something before child services does?

My 18 year old sister has a 2 month old son. She is basically wild and in my opinion not ready to be a parent. She's been promiscuous for years and honestly we aren't really sure if the baby's supposed father is indeed the father. There's been pictures floating around online of my sister drunk slobbering on other guys, while the baby's father is out of town working all week. She doesn't have a job and lives with my mom in a horrible situation. They live in a small mobile home with plywood covering holes in the floor. Out of 3 adults in the home one is on disability, another's on unemployment and she's on welfare for the baby. The step-dad is awful and my mom talks about leaving him all the time but of course has no money. There's nothing but insecurity in the home for the child. I'm afraid that child services is going to take my nephew. I don't know what to do. I don't think my sister would even listen to me. I told her numerous times before she needs to be more mature but there's a child involved now. I feel like I'm being nosy and intrusive if I say anything, but at the same time irresponsible if I don't.