I'm asking because I'm genuinely puzzled. 
I remember being 9 years old and my children being 9 years old, and there's no way any of us would have had the maturity to know that then.
I've heard people say they knew at a young age but why were they even thinking about that?
Here's the link I was just reading: https://www.stuff.co.nz/life-style/gender-and-society/300551963/auckland-mum-sets-up-social-group-so-younger-queer-children-can-be-themselves 
If you were to ask a child that young if they prefer their own sex to make friends with, of course they would say Yes, because they more often than not have more friends of the same sex before high school, from my experience. Some boys may have friends who are girls, and vice versa, but that doesn't necessarily mean they are gay.
And because they have no knowledge of sexual relationships at that age - how do they know they're gay?
If anyone has any personal experience of this that they wouldn't mind sharing, I'd really like to learn more.
I myself was never a 'girly-girl' who liked playing with dolls or dressing up in frilly clothes and I did think boys had more fun.
I was also more interested in Maths and Science, and still am.
But when I got older I wasn't attracted to females for sexual relationships - only men. And I'm married with 2 children.
*Edited to add* I went to an all girls school and as a teenager did have 'crushes' on older girls at the school but I think that's different, and maybe everyone has that experience as a teenager as they try to figure out who they are?
I remember being 9 years old and my children being 9 years old, and there's no way any of us would have had the maturity to know that then.
I've heard people say they knew at a young age but why were they even thinking about that?
Here's the link I was just reading: https://www.stuff.co.nz/life-style/gender-and-society/300551963/auckland-mum-sets-up-social-group-so-younger-queer-children-can-be-themselves 
If you were to ask a child that young if they prefer their own sex to make friends with, of course they would say Yes, because they more often than not have more friends of the same sex before high school, from my experience. Some boys may have friends who are girls, and vice versa, but that doesn't necessarily mean they are gay.
And because they have no knowledge of sexual relationships at that age - how do they know they're gay?
If anyone has any personal experience of this that they wouldn't mind sharing, I'd really like to learn more.
I myself was never a 'girly-girl' who liked playing with dolls or dressing up in frilly clothes and I did think boys had more fun.
I was also more interested in Maths and Science, and still am.
But when I got older I wasn't attracted to females for sexual relationships - only men. And I'm married with 2 children.
*Edited to add* I went to an all girls school and as a teenager did have 'crushes' on older girls at the school but I think that's different, and maybe everyone has that experience as a teenager as they try to figure out who they are?