Twin sisters married twin brothers. Now they all live together - and breastfeed each other's babies.

• TLC's show "Extreme Sisters" follows five duos who have close bonds with their siblings.
• One duo, Brittany and Briana, are identical twins and married identical twin brothers.
• They also had babies within four months of each other, who are genetically siblings.

When identical twins sisters Briana and Brittany Deane were teenagers, they hated each others' boyfriends.

"So often, we were in relationships with singletons who didn't understand our twin sister bond," Briana told Insider. She added that deep down, she and her sister had an ultimate dream to marry a set of identical twin brothers.

"I think there was some underlying stress that if one of us got too serious with a singleton guy, then it would ruin this dream we had, which was always our hope, even though others told us it was unrealistic," Brittany told Insider.

So when the duo met identical twin brothers Jeremy and Josh Salyers, they knew they'd found something special. The sisters went on to marry the brothers, Brittany with Josh and Briana with Jeremy.

Now, on the TLC show "Extreme Sisters," they're showing what it's like to all live under one roof and raise their babies, who are genetically siblings, together as one big family.

Brittany and Briana wear matching outfits every day

Like other "Extreme Sisters" duo Anna and Lucy, Brittany and Briana wear matching outfits daily, from dresses to pajamas to casual attire.

There's no routine for how the duo chooses outfits. According to Brittany, they usually wake up and have similar ideas about what to wear that day.

"More often than not, it's very much a joint effort. I think that because we have the same brain, we will both wake up thinking, 'OK, I want to wear X outfit today,' or whatever the event is that we have going on that day," said Brittany.

But when they aren't on the same page, it can feel upsetting, she said.

On the show, Brittany and Brianna run into another clothing-related hurdle when they move into their mansion together to join their families. Some of their matching outfits get misplaced, making getting ready for the day a complex task.

They view each other's babies as their own

Both couples decided to take a co-parenting approach to raising their two children: Brittany and Josh's five-month-old Jett, and Briana and Jeremy's one-month-old Jax.

"I feel like I'm Jett's parent and I think [my brother] feels the same way about Jax," Jeremy previously told Entertainment Tonight. "We all live together and we are raising the kids together. It feels like one family unit, not two separate couples with their own babies. It's the four of us with our two babies."

In fact, Brittany and Briana breastfed each other's babies during one episode.

They're still working out what their children will call each of them, but have thrown around ideas like "daddy" and "duncle," and "mom" and "aunt mom."

The couples struggle as they try to become more independent

Doubling up on parent duties has proven handy as both couples start to separate from their twins and learn to be more independent on the show.

During a recent episode, Brittany and Josh decided to go on a solo dinner date without Briana and Jeremy for the first time ever.

"Without Briana, I just feel a little bit insecure," Brittany said of the experience. "I feel like Josh is so cool and I'm just a dork."