Fraternal birth order and male sexual orientation

 I had heard of this effect some years ago.  Now it has a writeup on Wikipedia 

https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male_sexual_orientation 

I'm the third of the first three children, all sons.  I've even heard this called 'the third son effect'.  This doesn’t mean I think my younger brother is gay - note that it says "This does not mean that all or most sons will be gay after several male pregnancies, but rather, the odds of having a gay son increase…"   with each male pregnancy.