Next of Kin
Oblivion: Dark Brotherhood Quest
You'll find the next dead drop in a sack next to Chorrol's Great Oak tree. Your next target is a family that needs to die.
Some of the murders in this quest make it difficult to avoid a bounty. If you have any stolen goods that you'd like to keep, you may want to find a safe place to store them until you complete this quest.
Perennia Draconis
The first of the Draconis family lives in Applewatch, which is just west of Bruma. When you arrive, you'll find Perennia Draconis. If you talk to her, you can tell her that you're looking for her children. She assumes that you've been sent to deliver gifts to them, and she gives you a paper that details all of their whereabouts. Rather convenient. Once she's basically handed over their death certificates, take her (and her dog) out.
Now, it's time to find her children.
Andreas Draconis
Andreas is the barkeep of the Drunken Dragon Inn, northeast of Leyawiin. You'll need to have Andreas attack you to avoid a bounty, since a guard spends his time in the Inn with him. Tell him that his mother "bled like a pig" and he'll go after you. Let the guard deal with him.
Caelia Draconis
Caelia is a guard at Castle Leyawiin, but during the days she's guarding the upstairs rooms at the Three Sisters Inn. If you tell her you're there to kill her, she'll attack you.
Caelia is a guard, so be prepared for a decent fight.
Matthias Draconis
Matthias lives in the Imperial City Talos Plaza district. You can break into his house at night, although you'll need to sneak past his servant to avoid detection. Enter his bedroom and take him out.
You'll receive a bounty as soon as you attack Matthias. The only ways to avoid it are to place a poisoned apple on him, or to harass him enough until he attacks you.
Sibylla Draconis
Sibylla lives in Muck Valley Cavern. She'll attack you as soon as you enter the cavern, and she's not much of a challenge. Muck Valley Cavern is filled with many animals, including bears, so be cautious if venturing in.
Head to the Castle Skingrad courtyard and pull your next dead drop orders from the well. Along with your 500 gold reward, you'll receive your next quest, Broken Vows.