The Influence of Birth Order on Identity and Sexuality

National Siblings Day brings attention to the dynamics between siblings. Guest host Selena Simmons-Duffin explores how the order of birth, specifically the number of older brothers someone has, can impact their sexuality. This concept is known as the “fraternal birth order effect.”

Scientific research on sexuality has faced criticism for historical bias and inaccuracies, yet the fraternal birth order effect remains supported by data. This phenomenon suggests that the chance of a person identifying as gay increases with the number of older brothers they have. Studies from various countries, including Turkey, the United States, Brazil, and the Netherlands, have reached similar conclusions.

The podcast delves into what this effect is, its research history, and its limitations in explaining sexuality. The episode is part of NPR’s “Science of Siblings” series, which investigates the science behind sibling relationships. For more insights, listeners can explore similar stories within this series.

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The episode was produced by Rachel Carlson, edited by Rebecca Ramirez, with fact-checking by Brit Hanson, and audio engineering by Maggie Luthar.

Other intriguing topics from the “Science of Siblings” series include the origin story of National Sibling Day, the influence of a brother’s hormones on a sister while in the womb, and the diverging paths of identical twins growing up with autism.