Liam Pádraic Aiken (born January 7, 1990) is an American actor. He has starred in films such as "Stepmom" (1998), "Road to Perdition" (2002), and "Good Boy!" (2003), and played Klaus Baudelaire in "Lemony Snicket's A Series of Unfortunate Events" (2004), based on the series of books.
You can watch Aiken go through his tweens in his movies.