identical twin

English Thesaurus

1. either of two twins developed from the same fertilized ovum (having the same genetic material) (noun.person)

hypernym	:	twin,
definition	:	either of two offspring born at the same time from the same pregnancy (noun.person)

hyponym	:	conjoined twin, siamese twin,
definition	:	one of a pair of identical twins born with their bodies joined at some point (noun.person)