You may have heard the sexuality theory that gay men are more likely to have older brothers.
And unlike other theories, like finger length or if your hair grows counter-clockwise, scientists give this one some credibility.
Researchers call this phenomenon the fraternal birth order effect, or FBOE.
But now, scientists have suggested that having an older brother could mean cis gay men are more likely to prefer bottoming.
Two new studies published in 2018 – one conducted by in Canada and the other in the US – implies this could be the case.