'Extreme Sisters' Sneak Peek: New Moms Brittany and Brianna Breastfeed Each Other's Babies

Identical twins Brianna and Brittany also married identical twins, making their children genetic siblings

Sisters Brittany and Brianna Salyers truly share everything.

In PEOPLE's exclusive sneak peek at Sunday's season finale of Extreme Sisters, the identical twins reflect on becoming new moms together and reveal that they breastfeed each other's babies.

"So we're settling into our life as six of us," Brianna begins in the new clip.

"And parents of quaternary twins!" Brittany adds of their newborns, who are genetic siblings because the sisters married identical twin brothers, Josh and Jeremy Salyers.

"We're still working on what our children will call all of us," Brianna says. "Mommy and ammy works really well"

"So mom and aunt mom — mommy and ammy," her sister explains.

Though they add that they aren't as set on what the children will call Josh and Jeremy: "We've been talking about what are the dads going to be, daddy and dadsy, or daddy and duncle," Brianna says.

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Brianna then goes on to say that because they are identical twins, and their kids share the same DNA, they also share their nursing duties.

"One of the best things about having two moms in the house is that we have four boobs," she quips before continuing, "No it's that we can actually help each other nurse our babies."

"Which we do," she says. "We breastfeed each other's babies because we feel like they're both, both of our babies."

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"Do you think our milk tastes the same?" Brianna later asks as she feeds one of the babies. "I mean it must."

"I figure it does," Brittany responds.

"We share DNA so it's like we're producing the same milk," she tells the cameras. "It's just no big deal for us."

"It's the same thing," Brianna concludes.

The season finale of Extreme Sisters airs Sunday (10 p.m. ET) on TLC.