Siblings?

Because I REALLY like this movie I am holding it to a higher standard than most throw-away slasher films. That is why an inconsistency I noticed is bugging me.

When the Stranger has gotten loose and the younger sister 'invites' him upstairs they pan the fireplace mantle and a photo there implies that the Stranger is most likely their older brother.

It's a lingering shot so it definitely means something. So... if he's their brother, why doesn't he recognize the house?

I thought it was great that I had more patience. Turns out... I just don't give a sh!t