Aether have the Dark and Lumine have the Light elements.

I've noticed that in the trailer of the Collab with Ufotable Aether has black earring and all the other spots where his actual elemental resonance is shown, meanwhile Lumine has all spots white and so the light element. if we think about the name Lumine is linked with light like things, Lumen in Latin (in English kind of too) means light, lamp, bright so she may have the Light element Aether is the Greek primordial god of space, void, and light yes, but Aether was born form Erebus the personification of the Darkness and Nyx goddess of the Night. so maybe the twins have opposite powers like Ying and Yang...