when they were filming twilight there came up and created the cullen crest so the cullen could wear it as jewellery to tunjuk they are unity and a family! like rosalie would wear it as a necklace, alice a choker, carlsle and esme rings and edward, emmett +jasper a waistband. i think it a nice touch, like they came up with the tatoo for the Serigala Jadian to tunjuk their commintment for the pack to tunjuk their all "brothers" hope i helped!
