This study should come with a warning -- studies like this are always misrepresented in the press. But as long as you bear in mind that (a) disentangling genes, environment, and the interaction between them, is far from being an exact science, and (b) heed the researcher's caveat that this is only one of many factors involved, the study is intriguing. The study investigated twins' choice of spouses and close friends, and found a preference for a surprising degree of similarity. Participants answered a detailed questionnaire measuring social background, personality, and attitudes. Twins turned out to be as similar to
their spouses and friends as they were to their fraternal twins, though not as similar as they were to identical twins. The assumption does seem to be that what is true of twins is true of all of us, and you could make a case that twins might be more likely to seek out people like themselves, but still, it is interesting.