Study Shows Men With Older Brothers Are More Likely To Be Gay

In recent research, scientists are further exploring a compelling phenomenon: having one or more older brothers may increase a man's chances of being gay. This finding, known as the "sibling birth order effect," has been documented since the 1990s and has been observed and studied worldwide.

Scott Semenina, a psychology professor from Stetson University, noted in an interview with NPR that this pattern has been documented not only in Canada and the U.S., but also in countries such as Samoa, southern Mexico, Turkey and Brazil. According to Semenina, the theory is that the likelihood of being attracted to a man increases by about 331 TP3T for each additional brother he has.

The results of this study showed that men who had one brother had about a 2.61 TP3T chance of being gay. With a second brother, the odds increase by 331 TP3T to about 3.51 TP3T, while men with five brothers have about an 81 TP3T chance of being gay.

The underlying biological mechanisms behind this phenomenon have been studied for many years, including the potential association of parental chromosomes.2022 A study published in the Journal of Sex Research highlighted this correlation by examining data on more than 9 million people born in the Netherlands between 1940 and 1990.2023 The study found that a man with three brothers rather than three sisters was 41% more likely to enter a same-sex relationship if he had three brothers rather than three sisters. Researchers at the University of Melbourne found that a man's likelihood of entering a same-sex relationship increased by 411 TP3T if he had three older brothers rather than three older sisters, and by 801 TP3T if he had three older brothers rather than three younger brothers.

Study author Jan Kabatek told NPR that the findings were completely different from previous studies, and they also found that the same associations existed in women. This suggests that there may be some biological mechanism driving these associations, at least in part.

Despite this surprising finding, experts emphasize that this so-called pattern affects only a small minority of the general population. The vast majority of people with many older brothers will still be attracted to the opposite sex," Semenina noted. This study provides a deeper understanding of sexual diversity and reminds us that the formation of human behavior and sexual orientation is a complex process that is influenced by a variety of factors.