Thriller movie plot

Date: 10/18/2016

We were all part of a family with a bunch of children. All I can remember clearly was that I was one of the older sisters and there was one other older brother and a really quiet and sinister looking little brother. The little one never talked much and was always sulking around after our mom was murdered. He kept sending us this weird signals that the oldest brother was the culprit and making him out to be something evil/paranormal. But it was he himself who looked like the guilty one. Suffice it to say no one believed him. At the end, the little one turned out to be right because the oldest brother wanted to kill everyone.