Darius is the middle son of the current head of House Sakhavenid. He has a younger sister and an older brother. His older brother is to be the next head of the house. He and his sister dislike, pherhaps hate, their father. He has tried to marry them for political reasons, and even tried enrolling Darius in the army.
He and Layla, his sister, had promised to "run away" together. But Darius left alone, leaving her nothing more thana a letter, to join the thieves guild.