Who is Rulon T. "Uncle Rulon" Jeffs from Under the Banner of Heaven: A Story of Violent Faith and what is their importance?

"Uncle Rulon" is the leader of the polygamous sect, UEP. He was believed to be as powerful as Joseph Smith. It was reported that he had 75 wives and was the father of at least 65 children. Warren Jeffs, his son, become leader in Colorado City and Bountiful after his father's death.