<Li> Spencer Breslin as Cousin Derek: Sandra, Beth, and Bobby's stoner cousin and Martha's son . </Li> <Li> Gabe Steidl as Bobby Andersen: Sandra and Beth's little brother . </Li> <P> The film was scrutinized by the Toronto community for portraying the teenage murderers through a far too sympathetic lens . Author and journalist Bob Mitchel stated, "I don't think the movie dealt with how cold - blooded and calculating they were", in an interview about the theater adaptation of his book . </P> <P> The film received generally mixed reviews with a 27% rating on Rotten Tomatoes, and a 44% rating on Metacritic based on eight reviews . Dennis Harvey of Variety criticized the film for being "ineffectual and cartoonish", and compared it unfavorably to the similarly - themed 1994 film Heavenly Creatures . </P>

What is the movie the perfect sisters about