both are male
Aether, Erebus, and Nyx are all in a big ol' relationship together (it's a non sexual relationship, but still romantic, not platonic)
Aether and Erebus butt heads a lot tho, seeing as Erebus is darkness and shadow, and Aether is light and sky, but at the end of the day they are still really gay for each other (and Nyx)
Aether is slighty larger then Erebus.
Erebus's horns and hooves are made of obsidian and absorb all light around them, they are icy to the touch.
Aether's horns and hooves are Gold and radiate light and warmth.

Like Nyx, Erebus can control the shadows and darkness around him, he gives off a vibe of fear to others around him.
Aether controls light and gives a sensation of peace to everyone around him.