This is my line of thought:

Ares and Hephaestus are two of the more rejected Greek gods. Neither of them had many public shrines, and the other gods and goddesses tended to treat them poorly. Such as when Hera chucked Hephaestus to the earth and broke both his legs; and or when Hephaestus dragged Ares and Aphrodite naked to the gods.

They were both humiliated, ridiculed, and underestimated often; Hephaestus by the other gods, and Ares by both the gods and men. When the Greek gods fell out of humanity's favor, Ares approached Hephaestus with a convoluted plan to gain them the worship they each truly deserved. The two of them would work together to bring the gods back into mankind's favor. 

Of course, a few decades into their relationship, they started to argue and fight. A lot. The only person keeping the union together is Chike, who acts as a diplomat of sorts when the two bring up their conflicts of old.

That's what I was thinking when I made the two supporting characters for Polemos.