I'd probably just make him Lennox's son or one of hephestatus's slaves that Diana frees.?
Yeah, that's what I was thinking too. I would like to see one Hephaestus' closest apprentice come to Diana asking to learn more about his Amazon heritage. Then, Diana can of take him under her wing and convince the Amazons to let him have a crash-course on Amazon culture. The Amazons can give him weapons training and since he's skilled at crafting weapons, he can be a sort of weapons master and personally craft things for Diana. They could then do a story about him discovering his biological mom and he could keep learning from Hephaestus. I definitely think there are cool possibilities.