Board Thread:Consensus Track/@comment-28908658-20190217001843/@comment-6036561-20190217121811

Elveonora wrote: The reasons why the Tailed Beasts are referred to as it, are because:
 * they weren't conceived through the act of sexual reproduction, but magic
 * their genitalia haven't been shown

Everything Elveonora said, plus being them made out of pure chakra they will probably have no need to reproduce, hence the are probably agender (much like the angels in hebraic mythology)