Fraternal twins and identical twins differ in their genetic makeup. Fraternal twins are formed when two separate eggs are fertilized by two separate sperm and go on to develop into two separate embryos. Therefore, fraternal twins are genetically similar as regular siblings and usually share about 50% of their genetic material. If your DNA test results show two individuals with different profiles, that is indicative of the two individuals being related as fraternal twins.
Identical twins are formed when a single fertilized egg splits into two embryos. These twins share 100% of their genetic material and are, therefore, genetically identical. If your DNA test results show two individuals with the same DNA profile, that is indicative of the two individuals being related as identical twins.