As we all are now fully aware there is still the endless debate of Nature Vs. Nurture studies. Twins potentially provide us with one of the most powerful techniques available for separating the influenced of genetic and environmental factors, and on psychological and behavioral traits. This process is called twin studies, as Lilienfeld would state in our text the logic of twin studies rests on the fact that identical twins are more similar genetically than are fraternal twins, if identical twins are more alike on a psychological characteristic we can infer that this characteristic is genetically influenced.
There are several articles every year that assures us there's a link between homosexuality and biological features, the headlines imply that people are born with tendencies which will make them gay or lesbian and that change of sexual orientation would be impossible. The article had discovered that only about 38% of the time the identical twin brother would be a homosexual, however the public still believes that genes "nature" still play a major role in if one "chooses" to be homosexual or not.
studies have also shown that many family factors had a strong influence on the sexual preference of the specific twins in which were involved in this particular case study, therefore making homosexuality and environmental "nurture" factor. The study had also showed that the same family environment was perceived in different ways by identical twins, these differences later lead to homosexuality in one twin but not in the other.
in conclusion no specific study shows if homosexual twins are genetically influenced or if it is simply family factors, this will be an ongoing debate for generations to come it's one of those studies that may go even further than genes itself. Will we ever come to a conclusion? so far all hypotheses have been ruled out, and there are still many more being made.
Source: . Bailey, JM; Pillard,RC (1991): A genetic study of male sexual orientation. Arch. Gen. Psychiatry 48, 1089-1096