The most common type of twins are non-identical twins, which can be the same or different sexes. Non-identical twins are also known as ...MenuCloseHomeCOVID-19Arts+CultureBusiness+EconomyEducationEnvironment+EnergyHealthPolitics+SocietyScience+TechnologyTokyo2020EditionAfricaAustraliaCanadaCanada(français)EspañaFranceGlobalPerspectivesIndonesiaNewZealandUnitedKingdomUnitedStatesEdition:AvailableeditionsUnitedKingdomDonateGetnewsletterBecomeanauthorSignupasareaderSigninCOVID-19Arts+CultureBusiness+EconomyEducationEnvironment+EnergyHealthPolitics+SocietyScience+TechnologyTokyo2020Semi-identicaltwinssharealltheDNApassedonfromtheirmother,butonlyaportionfromtheirfather.Fromshutterstock.comHannahBrown,SouthAustralianHealth&MedicalResearchInstituteAuthorHannahBrownPostdoctoralResearchAffiliate,UniversityofAdelaide;ChiefScienceStoryteller,SouthAustralianHealth&MedicalResearchInstituteDisclosurestatementHannahBrowndoesnotworkfor,consult,ownsharesinorreceivefundingfromanycompanyororganisationthatwouldbenefitfromthisarticle,andhasdisclosednorelevantaffiliationsbeyondtheiracademicappointment.PartnersTheConversationUKreceivesfundingfromtheseorganisationsViewthefulllistEmailTwitterFacebookLinkedInWhatsAppMessengerWeallknowasetoftwins;perhapsevenasetofidenticaltwins.InAustralia,twinsaccountforaboutonein80births.ButinresearchfromtheUniversityofNewSouthWalesandtheQueenslandUniversityofTechnologypublishedtodayintheNewEnglandJournalofMedicine,welearnofaveryuniquesetofAustraliantwins.AboyandagirlfromBrisbane,agedfour,havebeenidentifiedasonlythesecondsetofsemi-identical,orsesquizygotictwins,intheworld.Theyarethefirsttohavebeenobservedinutero(inthewomb).Thisextremelyrarephenomenonistheresultoftwospermfertilisingthesameegg.Readmore:Seeingdouble:whytwinsaresoimportantforhealthandmedicalresearchHowdotwinsoccur?Themostcommontypeoftwinsarenon-identicaltwins,whichcanbethesameordifferentsexes.Non-identicaltwinsarealsoknownasfraternaltwinsordizygotictwins(fromtwozygotes,whatwecalltheearliestembr