It exists in places like Turkey and Brazil.” Known since the 1990s as the fraternal birth order effect, it has been theorized that men have roughly a 33% increased probability of being attracted ...

Some of the strongest current evidence that some people are born gay is based on a phenomenon called the fraternal birth order effect. Several peer-reviewed studies have shown that men with older ...

The more older brothers a boy has, the more likely he is to be gay when he grows up – an effect called the “fraternal birth order effect”. Now it seems that increasing levels of antibodies ...

The birth of twins in all human populations is ... However, evolutionary-based explanations of fraternal twinning offer insights into this relatively rare event. Twinning rates differ across ...

They settled down in Birmingham, England, eager to start a family. On July 3, 2006, Amanda gave birth to fraternal twin girls, and the ecstatic parents gave their daughters intertwined names ...

Researchers are further exploring the notion that having an older brother increases a man's chances of being gay. It's called fraternal birth order effect.