There are haunted places, and then there are haunted people. And these things will always target the weakest - mostly prepubescent girls if they are part of the family, but always the weakest. The fact that the demon has not only been hanging around your brother since he was a child but is now showing itself to your brother's child tells me that this thing has attached itself to him and his family.
It will not stop and the torment will escalate until your brother's family is destroyed. It will not just go away on it's own and it will not be ignored. This will get worse and worse without some kind of help.
I don't know what Christian denomination your family are affiliated with, but you need to go to either your priest or pastor and tell them what is going on. Do not stop seeking help until someone listens to you and believes you and is willing to help you.
Satan is real and demons are real and, like Scripture says, these things roam the earth, looking for whom they may devour. You definitely have a problem, it is very real, and your family is in danger.
Seek help immediately. It's the only way you will be able to get rid of this thing. Oh, and start praying for Jesus to intervene and deliver you from this, and keep praying and don't stop praying until this demon has been driven out.
Also, if you don't mind, and you remember, please FReepmail me with your progress. I will pray for you also.
I don't think my brother did until his first born has seen what he has.
When I talked to my family about taking the Bible literally, they scoffed. Not so much lately.