A fraternal twin is a sibling and therefore is related by 50% consanguinity. Fraternal twins are no more genetically similar than regular siblings. As identical twins come from the same zygote, their most recent common ancestor is each other. They are genetically identical and 100% consanguineous as they are separated by zero generations (formula_2). Twin studies have been conducted by scientists to examine the roles that genetics and environment play in the development of various traits. Such studies examine how often identical twins possess the same behavioral trait and compare it to how often fraternal twins possess the same trait. In other studies twins are raised in separate families, and studies compare the passing on of a behavioral trait by the family environment and the possession of a common trait between identical twins. This kind of study has revealed that for personality traits which are known to be heritable, genetics play a substantial role throughout life and an even larger role during early years.