My sister in law is so unfit to be a mother. She is a lunatic. Does not have a clue about anything. She didn't even know that the stroller and car seat had to be put together. This is not only problem she is mentally unstable and she is not capable of being a fit mother. I am scared for my nephew and want to take custody of him. Please help me this baby shouldn't suffer because his mother is unfit. She is 28 and can not handle anything in life.

Unfortunately unless you can prove she is unfit there isn't much of anything you can do.Not knowing how to put seats and strollers together isn't enough to prove that cause they will find a way and figure it out. Keep a record of all the things she does and when you have enough evidence together you can try to fight for custody. Until then it is just your opinion.

You will have to prove to a court that she is unfit. You CANNOT just take a baby from it's mother. She will have to do something or be doing something to have to give up her baby.
Does she know you feel this way. Have you talked about this with her? Or is she too lunatic to bring it up?

Has she been offered any help at all? What does your brother think of this if there still married?