If people wanted this to be known, they'd put it on their profile. If it's not there, they've probably got some decent reason for hiding it. Or they just like confusing people, in which case they'd only perpetuate the confusion in this thread.
But, hey, I'll humor you. I'm 17 and my gender is... wait, no I'm not. I... just turned 18. Which means... I'm finally safe from Pedobear!
...Though I still look like I'm 12...