Anime yu yu i hardly knew you (couldnt help it)

[vegeta rocker]

Curious, ok i know that hiei's sister can cry pearls, i heard that Hiei himself cries black gems. Is this true? And whats up with Hiei anyway, i know he got his jagan to find his sister but were the rules he couldnt tell his sister who he was or he just doesn't want to because if he died it would be hard for her. I say he couldn't but my sister says otherwise, so which one is it?
Since i haven't gone through the whole series yet i was wondering if they ever shed any light on who his dad was, besides him being a fire demon.
Thanks!