Identical twins are also called monozygotic twinsmonozygotic twinsFraternal twins are also dizygotic twins. They result from the fertilization of two separate eggs during the same pregnancy. Fraternal twins may be of the same or different sexes. ... In contrast, twins that result from the fertilization of a single egg that then splits in two are called monozygotic, or identical, twins.
› genetics-glossary › Fraternal-TwinsFraternal Twins - National Human Genome Research Institute. They result from the fertilization of a single egg with a single sperm. ... However, they are actually the result of fertilization of two different eggs, and thus can be different genders and look different, and have different characteristics.