Who is Dan Lafferty from Under the Banner of Heaven: A Story of Violent Faith and what is their importance?

Dan Lafferty is one of Ron's younger brothers and his accomplice in the Lafferty murders. Dan tells police that although it was Ron that received the removal revelation, it was Dan who actually did the killing. Like Ron, Dan is a member of Onias' School of the Prophets. Dan did not receive revelations the way the Ron did. When Ron shows Dan the removal revelation, Dan agrees to help him carry it out.