Can you join the dark brotherhood of you're a ware wolf?

To join the Dark Brotherhood you have to go to Windhelm and walk around until you hear a rumor about a house where a boy is staying and his mother was murdered. Pick the lock. Go in and talk to the kid, he'll tell you he wants you to kill Grelod the Kind at Honorhall Orphanage in Riften. Once you get to Riften enter the orphanage in sneak mode and wait for the opportune moment, Grelod will scream when she dies, alerting the children and Constance, so leave as soon as she's dead and return to the kid in Windhelm and tell him she's dead and he'll pay you. Leave Windhelm and enter any other city in Skyrim and you'll be given a letter by a courier, after you read the letter go to an Inn or your house (if you have one yet) and sleep. When you wake up listen to Astrid and she'll eventually tell you to kill one of the three captives in the room (I usually stand at one end of them with all three lined up and use Unrelenting Force to kill all three), it doesn't matt which one you choose.