Twins

Cause its hard to find them but they have used twins in cheaper by the dozern and 'desperate housewives' and also all the mary-kate and ashley films....

~~*AIM*~~
The world will look up and shout "Save us!"... And I'll whisper "No."

well in the case of this movie, the twin that played sopie would've had such a smaller part and paycheck than the one that played megan that they would probably not agree to it. Plus since sophie's part is so small, there's no reason to hire another actress

Also, it's interesting to know that Elisabeth Harnois had already played twins before, in an episode of Criminal Minds a couple of years earlier.

because there probably aren't that many sets of twins who act. i doubt its a money issue because most movies try to have scenes showing the twins together and when using one actor, that'll cost more because of the effects needed and the extra footage since they gotta film scenes twice over.

All the ones everyone has mentioned and also not a lot acting twins maybe one out of the two but rarely both unless parents made them at a young age. There are a few actors who are twins and most people are unaware including Linda Hamilton from Terminator and Nicholas Brendon from Buffy, the other twin just didn't act as they are two different people.

I know this post is really, really old... but I found it kind of funny that no one mentioned that Shawn Ashmore, who plays Christian in the movie, is a twin and his brother Aaron is an actor as well. I'm sure that is well known, it just wasn't mentioned here.