Tammy: Actually, genetics don’t apply to Daine: her father’s godhood overrides any mortal magic she would or would not have had.
As far as Numair’s family, as I understand it the Gift pops up to greater or lesser extent throughout his family tree on both sides, sometimes in such a small amount that it’s very limited in its use. That much is genetic, but body chemistry can amplify or expand the amount, while training can strengthen it and build it up.
He has a very large, extended family in Tyra. He couldn’t visit them for years, though, because when he went home after things went bad for his friendship with Ozorne, Ozorne’s trackers tried to kill him there and nearly killed members of his family (and they lost a couple of houses in the fire). He fled to keep his family safe. He’s been home, once or twice with Daine, since Ozorne’s death. I’m not sure where they’re holding the baby’s naming. That’s not something Aly could find out where she is at the moment, and all of my Daine/Numair news is stuff that Aly hears.