Yes, I believe there are only two genders (that's excluding non-binary). I am forever wondering whether to call non-binary the third gender or simply treat it as a separate entity completely! Gender is a man-made construct and since we only thought up two genders, male and female, in my mind that settles it! If you don't identify with either gender, you're non-binary. That's the way I look at it, although I will admit that I am highly uneducated in the matter, yet open-minded, and will happily listen to anyone who thinks I am mistaken, mislead or disagrees.