The Strangers theory

[Dr. Briggs]

There has been something I've really wanted to get off my chest for a looong time concerning one of my favorite horror films of this decade: The Strangers.

I know one of the big reasons people like this is due to it's lack of "ancient-curse, revenge-scheme, so-and-so-is-the-killer" plot twists and the like, but after watching it a few times something hit me really hard:

What if Sack-Head is James's brother?

The first big clue that caught my eye was the height-chart you saw on the wall for a few seconds at the house - Showing James's height as compared to one "Stephen"'s. Why would they film such a shot unless it was to drop hints as to the killer's identity? (Unless, of course it was for the very reason of provoking red-herring theories? X) )

Second thing I thought of was the fact that you could initially suspect James himself as one of the killers, until you see Sack Head actually run towards him.

Third:
And I turned 21 in prison, doin' life without parole
No one could steer me right, but mama tried, mama tried
Mama tried to raise me better, but her pleadin' I denied
That leaves no one but me to blame cause mama tried. - Sung by "The Strangers". Hints to possible family flashbacks in the sequel

Fourth: Though it kinda ruins the "It could happen to anyone" vibe, maybe they chose the summer house as Sack-Head/Stephen knew of a secluded house.

Fifth: Quite simply the look of utter, dumbfounded defeat on James's face as he sees Sack-Head remove his mask.

So, what does everyone think?