Ah...the other pairing, now this is Topaz to your left and of course Rhas al Ghul to your right.
We are still working our way through this one but we know this, Onyx is immortal with out the Lazarus Pit. Onyx is their son and his father has not done much to be a part of his life...and that is just fine with his mother of course and his two aunts.
Onyx is well traveled, he has lived in some very distant places and is slow to anger but wields great magical power. Having spent time with Dr. Fates and Strange he is known in the magical circles.
More later as we really haven't developed this one as much as the other...