Pop culture has given us many endearing sets of twins. Thompson and Thomson from Tintin. Mary-Kate and Ashley Olsen. Those crazy magicians Christian Bale played in The Prestige.
Perhaps my favourite was book 100, which told the story of Margo, an evil killer who looked just liked the twins, and decided to murder Elizabeth and steal her identity. A check of Wikipedia indicates that in true soapie style, Margo had her own twin, an equally evil killer named Nora. Further checking has led me to discover that *gasp* Francine Pascal is writing another book, to be published next year. Called Sweet Valley Confidential, it will look at the characters in their late 20s and early 30s. There's my reading list for 2011 covered.