If you get it down to two, and are friends with at least one of the people, then you can talk to your friend to convince them to strike out against the “assassin.” Then you just have to kill the lone survivor. You just have to make sure that no one has a line of sight on you when you kill them. They should all die in one hit unless something fairly weird (and buggy) happens. Note that it’s actually really easy, if you want the five second guide. This is probably the most interesting of the Dark Brotherhood missions.
