identical twin
From Longman Dictionary of Contemporary EnglishRelated topics: Microbes, genetics, biochemidentical twiniˌdentical ˈtwin noun [countable usually plural] SAMEFAMILYone of a pair of brothers or sisters born at the same time, who develop from the same egg and look almost exactly alike → fraternal twinExamples from the Corpusidentical twin• Enlarged ventricles have been found in an identical twin who develops schizophrenia, compared to the one who does not.