norest4thewicked
True Crime Writer
You know what, I think she screamed at the beginning of the abduction and that is why the bro looked out.
I think that's a good possibility - a quick, frightened scream when this man first came up to her. The brother probably was sleeping and it jarred him, he got up and looked out the window, was still sleepy and thought that the sister was with the ex, and just went back to sleep or laid there until he went to investigate further.