Paternal and maternal twins, commonly known as fraternal and identical twins, are distinguished by the different ways the multiple pregnancy begins. Identical twins begin as a single zygote that splits into two or more developing embryos. Fraternal twins are usually the result of multiple eggs being present for fertilization.
Because of their common origin, identical twins share a genome and are genetically indistinguishable. Despite this underlying similarity, superficial features such as fingerprints still vary between them. Fraternal twins, arising from separate zygotes with their own unique complement of genes, do not share a genome and are no more closely related to each other than any other siblings.