They're still in the middle of a criminal investigation -- but the polygamist family featured on "
Sister Wives" has officially agreed to do another season of their
TLC reality show.

The
Kody family -- 21 members strong -- drew the eye of Utah officials right after their show debuted earlier this year. Authorities completed an investigation and turned the case over to the County Attorney ... who will ultimately decide whether or not to prosecute the family for bigamy.
Season 2 is set to debut in March -- no word if the family will address the investigation on the show.
MMA superstar
Daniel Puder was in the house for
TMZ Live -- and talked to Harvey about the thousands of emails he's been receiving since he
offered up his address on TMZ to anyone being bullied.

Plus: Daniel talks
Mel Gibson,
Lindsay Lohan, and "
Sister Wives."
"
Sister Wives" star
Kody Brown has every aspect of his life filmed for a reality show -- but TMZ has learned when he got hitched to wife #4, a number of his polygamist guests were not nearly as camera-ready.

As TMZ first reported, Brown
married Robyn Sullivan a few months back. TLC's cameras were not allowed in the actual religious ceremony, but they did film the reception. But here's the problem ... About half the polygamist guests did not want their faces on camera because of the legal issues in which Kody now finds himself embroiled.
So Kody made accommodations by creating "camera-free zones" -- where lots of publicity-shy well-wishers hung out. As one person said, "The reality is that bigamy is still a felony and the mainstream still doesn't accept it."
As for the particulars of the reception, sources tell us there were about 200 guests ... mostly other polygamists. They served finger foods, open faced sandwiches, relish trays, and lots of varieties of cheesecake.
One of the plural family guests had their son and daughter sing a song for everyone -- "We Are Families," perhaps?
"
Sister Wives" star
Kody Brown spent some quality time with his newest bride,
Robyn Sullivan, by going perfume shopping at a mall in Utah in yesterday.

Scent of a sister wife.
Kody Brown officially has 21 mouths to feed ... TMZ has learned the "
Sister Wives" polygamist has married his latest fiancée
Robyn Sullivan ... increasing his total number of wives to FOUR.

Sources close to the "
Sister Wives" stars tell us the two were married "a few months ago" at a private religious ceremony in Utah.
Robyn isn't entering the family by herself -- she has three kids from a previous marriage who will join Kody's 13 kids and three
other wives.
We're told
TLC cameras were not allowed to capture the actual ceremony -- but the reception WILL be featured on the reality show. We're told some of the drama leading up to the wedding will be featured on this Sunday's episode.
With 21 total members, Kody can literally split the family in half and hold a regulation football game ... as long as he plays all-time quarterback.
Oprah's travel budget just took a pretty big hit -- TMZ has learned several members of the 21-member polygamist family from "
Sister Wives" just rolled over to Chicago to tape a spot for O's TV show.

Sources connected to the production tell us
Kody Brown, his multiple wives and "some" of his 16 children blew into the Windy City a few days ago to be interviewed by the Queen of Daytime for an episode set to air next week.
Oprah's no stranger to the topic -- just last year, she interviewed another polygamous family during an entire hour dedicated to exploring the world of plural marriages.
YOU get a wife! YOU get a wife! EVERYBODY gets a WIFE!
Kody Brown better not have any skeletons in his many closets ... because a TMZ review of Utah bigamy cases reveals no one -- at least no one we could find -- has ever been
prosecuted for bigamy in recent times ... unless the perp was suspected of a collateral crime such as child endangerment.

Law enforcement sources tell us there are so many polygamous families in Utah, that officials simply don't have the resources to go after all of them ... unless they're made aware of a more serious crime ... such as a the taking of a child bride, false imprisonment or anything violent.
As we previously reported, the Brown family -- featured on the TLC show "
Sister Wives" -- is currently at the center of a bigamy investigation ... and could face up to 5 years in prison if convicted.
The case is currently in the hands of the Utah County Attorney's office -- and the guy in charge,
Jeff Buhman, tells us, "
In my experience ... there has never been a traditional polygamist family
charged with the sole crime of bigamy."
The gorgeous brides of TLC's polygamous family reality TV series "
Sister Wives" (Meri, Janelle, Christine and fiancée Robyn) all gathered as one big happy extended family at an event in Beverly Hills recently.

The question is...
Kody Brown and wives have a powerful new legal force behind them -- TMZ has learned ... constitutional law guru
Jonathan Turley is now representing the "
Sister Wives" family in the polygamy investigation, and he's willing to fight it all the way.

Turley -- a professor at
The George Washington University Law School -- tells TMZ he is ready, willing and able to sit down with the Utah County Attorney and make a case why his clients should not be prosecuted.
Turley says absent some proof that the family is engaged in child abuse or other crimes, Utah prosecutors almost never prosecute for polygamy. Turley is quick to note there is absolutely no evidence of child abuse or other crimes in the Brown family.
Turley points out ... although Utah prosecutors have a lot of discretion in deciding when to prosecute someone, people can't be hauled into the criminal justice system simply because they've gone on TV and become high profile. In legalese, it's called "selective prosecution" ... and it's illegal.
Turley says his goal is to convince prosecutors to leave the Brown family alone. But he says if his clients are prosecuted, he'll fight it hard. Turley would not say outright that he'll make this a test case and push it all the way to the U.S. Supreme Court, but he made it clear ... he will do everything it takes to clear his clients if they're prosecuted.
The fate of the polygamist family featured in the TLC show "
Sister Wives" is now in the hands of county prosecutors ... TMZ has learned.

The Utah County Attorney has confirmed ... the Lehi Police Department has completed their felony bigamy investigation into
Kody Brown and his gigantic family -- and the case has been turned over to the Utah County Attorney ... who will ultimately decide whether or not to charge the family with a crime.
In Utah, bigamy can get you 5 years in prison ... though it's rarely prosecuted.
Kody Brown -- who has 3 wives, a fiancée and 13 children -- claims he was aware of the risk he was taking when he decided to put his family on the TLC reality show ... but insists it was a "
risk worth taking."