Voids "brother"! He's not his real brother, but Void and Devlin are brothers in demon standards. As in the lore of my story, no demons have siblings or were even born (they don't even have parents), but some may create their own families out of boredom and loneliness. Or even refer each other to acquaintances.
Void doesn't see Devlin as a fully fledged demon, as he's always assing around, doing random things.
On Earth he's always drunk, playing video games or watching anime, has no job and is a complete hermit. He tends to shut himself out from the world, living off Voids hard earned money, which of course drives Void up the fucking wall... XD And that's rare for Void to even show a tiny bit of emotion.