Quote Originally Posted by Azurymber View Post
from ff wiki: "Final Fantasy XIV gives exposition to the elusive male viera, who are virtually identical at birth to females; only upon maturing they are able to be identified gender wise."

So there is lore saying they are almost identical.
Can make up lore saying that some males choose to dress/live as "females" to remain with them. And others choose to be more masculine and leave.
Same lore is also stating that when the Male Viera come to breed they take every boy having reach maturity as wards.