The show stars a 41-year-old ad salesman, Kody Brown, and his four wives, 13 children and three stepchildren. Brown is legally married to one of the women, Meri Paul, but he refers to all of them as his spouses. All five are fundamentalist Mormons who call their lifestyle "plural marriage," a practice the official Mormon church outlawed in the 19th century.
"It's generally known in the community there are polygamists in Utah County," deputy Utah County attorney Julia Thomas told The Salt Lake Tribune. "The problem is we typically don't have them on TV admitting to breaking the law. We are being confronted with it in a very public manner."
In Utah, bigamy -- being married to more than one person at the same time -- is a third-degree felony, punishable with up to five years in prison. The state law also says someone can be found guilty of bigamy through cohabitation with multiple partners even without a legal marriage.
But authorities rarely prosecute polygamists like Brown, who is one of an estimated 38,000 fundamentalist Mormons who practice polygamy.
"It's been our policy -- because of resources -- that we would focus on the most serious crimes," Paul Murphy, a spokesman for the state attorney general's office, told the Tribune. "In the past eight or nine years, we have been looking at crimes involving child abuse, incest, fraud and domestic violence."
Brown and his wives have no prior criminal convictions or charges. "Do we want to spend state resources prosecuting these people and putting the kids in foster care?" Murphy was quoted as saying.
Utah's last bigamy conviction was in 2001, when one of the state's most high-profile polygamists, Tom Green, was sent to jail for bigamy and failure to pay child support. He was later also found guilty of child rape, Utah's KSL TV station reported.
After learning of the investigation, the Brown family issued a statement on Tuesday explaining their motives for exposing their lifestyle on TV.
"When we decided to do this show, we knew there would be risks," the statement said, according to the Philadelphia Daily News. "But for the sake of our family, and most importantly, our kids, we felt it was a risk worth taking."
The Brown family also appeared recently on ABC News' "Nightline" program, explaining why they decided to star in the reality TV show.
"We aren't saying this is for everybody," the second wife, Janelle, said. "We don't even recommend it for anybody who's not interested."
Kody Brown said he sleeps in a different wife's bed each night, and that his Mormon beliefs led him to a polygamous lifestyle.
"I just fell in love, and then I fell in love again, and then again," he told ABC. "My belief kind of pushed me in that direction. But in retrospect, I would go all the way back saying I do it for love because this is something that's come together out of love."