From Longman Dictionary of Contemporary Englishidentical 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 twin
Examples from the Corpus
identical twin• Enlarged ventricles have been found in an identical twin who develops schizophrenia, compared to the one who does not.• If one identical twin is gay, the chances that his brother is also gay are 50 percent. 