Why do gay people have gay siblings

But pregnant women sometimes also produce antibodies against fetal molecules — for example, if their fetus has a different blood group. The team collected blood from women, and screened it for antibodies to a particular brain protein that is only made in males. They thought this would be a good candidate, because it plays an important role in how neurons communicate with each other, and because it is produced on the surface of brain cells, making it relatively easy for antibodies to find and detect it.

Gay people often have older brothers. Why? And does it matter?

Compelled by society to enter marriages and have children, their reproduction rates may have been higher than they are now. How many gay people have children also depends on how you define being "gay". Many of the "straight" men who have sex with fa'afafine in Samoa go on to get married and have children.

Men with older brothers are more likely to be gay, study suggests

The spectrums of sexuality and gender are complex and influenced by many different factors. Image via Shutterstock Sexual orientation vs. How does genetics affect sexuality? What else influences sexual orientation? Ganna et al. Archives of Sexual Behavior. Handbook of Behavior Genetics , Chapter Community Genetics.

We may know why younger brothers are more likely to be gay

The findings showed that men with older siblings are more likely to identify as gay, with the probability increasing with the number of older brothers they have. The researchers also found that this correlation does not extend to lesbians and older siblings or bisexuality.