I'm completely convinced Qetesh is the mc's mom. Qetesh had an affair with a mortal around the same time mc was born, Mc's mom was a mysterious Qetesh "priestess" who just magically appeared in the woods one day. Quetesh statue shows up to save the mc when Ziva was going to kill him over the pregnancy thing. And he calls Quetesh mom when she first appears
I think Ziva is just a regular priestess, honestly I don't think they look alike, they're just both dark skinned. And Quetesh is dark skinned only because she's based off an Egyptian goddess.