Short answers, pulled from the story.
Sexual orientation is an enduring pattern of romantic or sexual attraction to persons of the opposite sex, the same sex, or both. The core attractions forming the basis of adult sexual orientation typically emerge between middle childhood and early adolescence.
The fraternal birth order effect is a phenomenon where the probability of a male growing up to be gay increases with each older brother he has from the same mother. This prenatal biological mechanism increases the odds of the next son being gay by 38 to 48 percent and may account for between 15 and 29 percent of gay men.
Alfred Kinsey, Wardell Pomeroy, and Clyde Martin published Sexual Behavior in the Human Male on the 28th of June 1948. They introduced the Kinsey scale, a seven-point rating system that challenged the binary assumption that people were either exclusively heterosexual or exclusively homosexual.
Alfred Kinsey was a scientist who published Sexual Behavior in the Human Male on the 28th of June 1948 alongside Wardell Pomeroy and Clyde Martin. His work introduced the Kinsey scale and forced a reevaluation of how society understood sexual orientation by revealing that attraction and behavior existed on a continuum.
The maternal immunization hypothesis is a prenatal biological mechanism where the mother's immune system builds antibodies to Y-proteins from a male fetus. These antibodies are later released on future male fetuses, interfering with the masculinization process and leaving regions of the brain responsible for sexual orientation in a default female-typical arrangement.
The concept of sexual orientation as an identity gained traction through the work of sexologists like Magnus Hirschfeld, who published a scheme in 1896. Thinkers like Karl Heinrich Ulrichs also began to categorize men into groups such as dionings and urnings in the late nineteenth century.