June and Jennifer Gibbons were identical twins who, from a very young age, were so bonded to one another that they created their own “twin language” to communicate speaking only to one another.  They rejected any other relationships including their own parents and siblings.  Later, they would construct a fantasy world that only they inhabited.  This lead to more serious anti-social behavior that resulted in a shocking crime spree.   Resources: Marjorie Wallace, The Silent Twins, (London, Vintage Books 1998).  BBC: Inside Story, The Silent Twin: Without my Shadow. YouTube, Uploaded by GottaFindPants, Nov 20, 2017. https://youtu.be/98WtP1qC61s  Music credits: Music from https://filmmusic.io: "Reflections" by Alexander Nakarada (https://www.serpentsoundstudios.com/) Licence: CC BY (http://creativecommons.org/licenses/by/4.0/)