Andreas Draconis is a member of the Draconis family. You have to kill every single member of the family to complete a quest for the Dark Brotherhood. You receive this quest from Lucien Lachance and as a reward you receive 500 gold. Andreas lives in Blackwood, in his Inn: 'The Drunken Dragon'. It's usually just him and the Imperial Legion Forester that hangs around downstairs, it's best to kill Andreas when he sleeps upstairs away from the guard. If you say that you killed his mother he will attack. This means it will not count as amurder so your Infamy and Bounty will not rise. It also means the guard will help you.