Nope, that's just the English translation. Japanese language has genderless pronouns, their word for he/she is "ano ko" or "ano hito" which literally means "that child" and "that person". The mangaka has deliberately left Crona androgynous, and I don't think he's about to change that.
They never tell in the anime, since Japanese has genderless pronouns the english translators just had to pick one or the other and they usually pick "he". My friend said they call him a boy somewhere in the manga but haven't checked myself
Me too.The lack of underwear kind of tipped me over there! Actually Crona's a boy... Bah! Even I couldn't decide which to put on him... her, uh! Hmmm..... I also agree that you need more clothing and you need to separate them too. Maybe you could do better next time!♪ ^_^