Cuel started off a newborn mortal. However, the winter was harsh and so he did not survive. His innocent soul traveled to, Novela, the land of the gods. Where he was transformed into two demons Cuel and Lo.
Cuel and Lo became the sons of the God of Deat., They were given the title The Brother Grim, with the purpose of collecting souls to feed the demons of The Underworld.
Yet, they were give one simple rule, never kill a mortal. Lo did not listen, and thus caused Cuel to be banished, until he has destroyed his brother. Now, Cuel wanders the Isles looking for his brother and a place to live while hidding his true identity.
Wait for me my darling. I will come back to you.
Do you seriously think I am butler material?