Sister Wives : Kody Brown and His 4 Wives Discuss 'The Principle' — What It Is and Why It Matters

Sister Wives: Kody Brown and His Wives Discuss 'The Principle' — What It Is and Why It Matters

Sister Wives: Kody Brown and His Wives Discuss 'The Principle' — What It Is and Why It Matters

Despite the highs and lows that their unconventional family unit faces, the Sister Wives remain devoted to their commitment.

On Sunday, Kody Brown and his four wives — Christine, Janelle, Meri and Robyn — will return to TLC for their hit series' 10th season. But although they're one family (Kody and the women have a combined 18 children), they are living apart from one another in four separate, temporary homes in Flagstaff, Arizona — and their bond is suffering as a result.

In PEOPLE's exclusive sneak peek at the premiere, Janelle invites Kody and her three fellow sister wives to lunch, where she poses a weighty and convicting question to the group: "Why did you enter The Principle?"

RELATED: Sister Wives' Christine Brown Wants to Move Back to Utah — 'I Can't Do Marriage with Kody Anymore'

TLC Sister Wives

"Whoa," Robyn tells cameras about her response to the query as Meri ponders, "I wonder where she's going with this."

Admittedly "surprised," Christine says in a confessional that she had no idea what Janelle was going to ask when she invited them to the meal.

So just what is The Principle and why does it matter?

"The Principle for us is the real term for plural marriage — it's the principle of plural marriage," Janelle explains. "I mean, it's really a gospel principle for us. So, in our community it's shortened to The Principle."

"The whole purpose we truly believe of living plural marriage is that you have to learn how to not be selfish," she adds.

For Janelle, she entered plural marriage "because I loved the whole idea of the whole family and this whole group synergy," she tells the table. "And I really felt like we would get progression, right? The whole idea is that we overcome our crap."

As for Meri, she was raised in it. "My dad took his first plural wife when I was like, 11 years old," she explains to viewers. "I had a lot of years with other moms and other siblings that weren't just from my mom. So it wasn't out of the ordinary for me."

Similarly, Christine "liked the sisterhood" of it. "To me, that's what family was, was a lot of grandmas. And then I had two moms, and so that's what a normal family was to me was a lot of moms," she says.

Robyn, who married into the family in 2010, was drawn to it because "the big family thing was always really cool to me," she shares with the group. "I loved when I first met you guys how you guys functioned. I loved it."

Speaking with PEOPLE ahead of the show's return, the women described The Principle in their own words.

Janelle

Janelle Brown/Instagram Janelle Brown

The Principle is what we call plural marriage. We feel like it's the principle of plural marriage, it is a religious doctrine for us. So we shorthand it a lot when we talk to each other about The Principle. And you know, for me, it presented an opportunity for self improvement, for self-betterment. I had a testimony — I gained a spiritual testimony, I believe, that I belonged in this family. And there's been a lot of growth. You get your edges knocked off when you have to work on so many relationships simultaneously. And you have to get over yourself and you have to learn how to not compare. I feel like I've grown in very positive ways as a person by living in this family.

Meri

Meri Brown/Instagram Meri Brown

Like Janelle said, it's just the principle of plural marriage. It's a common term amongst plural families who are doing it for a religious purpose. When Kody and I first got married, we discussed that this was something that we planned to do in the future with our family. And here we are now. It has been really good. There's been a lot of years of ups and downs for sure. Lots and lots of experiences, good experiences. You do get a chance to just kind of really be — what's the word? Introspective, I guess? And just figure you out and also figure you out in the context of the whole family. And what you can do to improve the family structure and just do your best to improve yourself, and then also the family. There's a lot of learning experiences and growth that comes in a family structure like this. I always say, "If you don't have the hard things, you're not gonna learn. When you do the easy things, you're not gonna improve."

Robyn

Robyn Brown/Instagram Robyn Brown

When we decided to live The Principle of plural marriage, we were making a promise to each other that we're going to work out this family together. That we're going to let go of all of our single woman type of struggles and desires, and kind of look out for the greater good and the bigger picture. It's sort of anti-culture ... Like, the monogamous culture is very much about a woman looking out for herself and her own. I think that a plural marriage — if you live it the right way — can be very free. You're looking out for other women as well, and that's very important to be doing, I think, across the board, whether you're in a monogamous world or a polygamist world. Looking out for the women in your life is very important to be doing. And I think that's our biggest thing, that we're making that promise to look out for each other, and then living that promise every day.

Christine

Christine Brown/Instagram Christine Brown

The Principle is like an ideal: In the end, what do you want this to be? It's kind of like the dream and the vision of all of us, in the end, sitting in our property, as grandparents. Closer, tighter bond, certainly. I had two moms growing up and I loved it.I wanted that for my kids, and we had this community that was incredible when I was a kid. I really wanted that for my children. There's just a great way to raise kids where you have all these people working together to create well-rounded kids. And I think our kids are amazing and phenomenal.

And it's so funny; the term The Principle is a term that we just throw out there because to us, it does mean the principle of plural marriage is the law, but it's almost like the term sister wife. When they first said that they were thinking of calling our show Sister Wives, I was like, "That's the dumbest thing I've ever heard in my life." Because it's a term that we know really, really well. But the rest of the world doesn't really know it. I told my sister, who doesn't live plural marriage, "They want to call our show Sister Wives." And she goes, "That's a really good idea. Go with that." Because no one knows what that means, and what it is is this relationship that people are obsessed with. It's so cute now, people use it in common language. So they use this sister wife, and whenever we see it in a movie or something we get super, super excited, and when we hear that girls refer to their best friend as their sister wife, it's like the biggest compliment. I don't know what The Principle is going to turn into necessarily, but it's been a fun evolution of that word, anyway.

Sister Wives season 10 premieres Sunday at 10 p.m. ET on TLC.