Many people believe that Seiya (and his two brothers for that matter) are not men, but women. This is untrue. Yes, it is true that Seiya (and Yaten and Taiki) can transform into the Sailor Starlights, let me explain a little bit for you.
Once upon a time, the Sailor Starlights lived on their planet with their Princess Kakyuu. But, Galaxia and her Animates challenged the Princess and her planet in what was come to be known as the Sailor Wars. Sometime after, the Princess disappeared, so the Starlights went to look for her on Earth.
On Earth, they were reborn as the three men Kou Seiya, Kou Yaten, and Kou Taiki, also known as the idol group the Three Lights. And despite their somewhat feminine appearence, they are all men (in one ep, you see all of them with their shirts off, and I doubt ANY GIRL could be THAT flat...). They were reborn as men. Therefore, they are men. With makes Seiya A MAN.
The only time Seiya is NOT a man is when he transforms into Starfighter... you can even "see" Fighter "grow"... uh... body parts. Starfighter is a female. Seiya is not.
So, get it through your heads... Seiya is a Man! And, now we will prove to you that Seiya is not only a man, Seiya is THE Man!