Many people have left the Mormon church. They are called, "Post-Mormon". They gather in coffee shops - as coffee and tea are forbidden by the Mormon church. These young people are asking questions about the Mormon religion that they are not allowed to ask.
The founder of the Mormonism religion, which for decades promoted and supported polygamy, had as many as 40 wives including one who was only 14.
The revelation was disclosed by the US-based Mormon church in an online statement.
Joseph Smith founded the Church of the Latter-day Saints, Mormonism's formal name, in the 1820s and was regarded by followers as a prophet.
"Latter-day Saints understood that they were living in the latter days (when) ancient principles would be restored to the earth," the online statement said.
"Plural marriage was one of those ancient principles," it said.
The church also revealed some of Smith's wives were already married.
"Plural marriage tested faith and provoked controversy and opposition," it said.
The New York Times first reported the disclosure, and said Smith may not have had sex with all the wives because some were "sealed" to him only for the next life.
The Mormon essay said the youngest of the women "sealed" to Smith was just 14.
The church defended the arrangement in its statement.
"Marriage at such an age, inappropriate by today's standards, was legal in that era, and some women married in their mid-teens," the online statement said.
"An angel appeared to (Smith) three times between 1834 and 1842 and commanded him to proceed with plural marriage when he hesitated to move forward," it said.
During the third visit, the angel supposedly threatened to kill Smith with a sword, unless he obeyed the commandment.
Smith had long been portrayed by the church as a loyal partner to his first wife Emma.
An official Church of the Latter-day Saints website stated the practice was not legal.
"The practice of polygamy is strictly prohibited ... as it has been for over a century," it said.
However, polygamy was part of the church's teachings for 50 years during the religion's early days.
The Mormon church claimed 15 million members worldwide, including 6 million in the United States.
The faith is also known for its practice of sending young missionaries around the world.