Nate Berkus and Jeremiah Brent Worried About Going From 1 Child to 2: It's 'About to All Shift'

Nate Berkus and Jeremiah Brent welcomed their second child, son Oskar Michael, via surrogate on March 26

Before they welcomed son Oskar Michael on March 26, Nate Berkus and Jeremiah Brent were anticipating what it would be like to parent two kids under the age of 3.

In a sneak peek of the season 2 premiere of their TLC show, Nate and Jeremiah By Design, the stars discuss what they can expect as a family of four.

“Anything right now that’s uncertain with us on the precipice of having another child just stresses me out on another level,” Brent, 33, tells husband Berkus.

“We’ve kind of gotten into this beautiful rhythm with Poppy, the three of us with this cute synergy. And that’s about to all shift,” Brent, 46, shares with viewers. “The baby will bring their own energy and dynamic to the house. But we’re all excited about it.”

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Nate Berkus and Jeremiah Brent

RELATED GALLERY: 19 Sweet Pics of Nate Berkus and Jeremiah Brent’s Daughter Poppy That Are Almost Too Cute to Handle

Also in the exclusive first look, the couple raves about their older child, who turned 3 on March 23. “We have a 2½-year-old!” Brent says as Berkus agrees, “I know, it’s so crazy.”

The pair recalls a sassy moment that occurred when Brent attempted to discipline Poppy.

“[Poppy] has a distinct personality and wants and needs and desires. And is not afraid to communicate them,” Berkus says. “The other day she said to Jeremiah, while she was in trouble, he said, ‘Poppy, it’s not funny.’ And Poppy goes, ‘It’s a little funny.’ ”

Berkus later jokingly tells Brent, “She’s running around the house like she owns it. She’s you with long hair.”

WATCH: Meet Nate Berkus and Jeremiah Brent’s Baby Boy, Oskar! Why He’s Named After Berkus’ Late Partner

The interior designers welcomed their second child via surrogate. Berkus and Brent chose their son’s name as a tribute to Berkus’ former partner Fernando Bengoechea, who died tragically in the 2004 Sri Lankan tsunami.

“His middle name was Oskar,” Berkus told PEOPLE exclusively of the poignant inspiration — and what’s more surprising, the tribute “was actually Jeremiah’s idea.”

“We have always honored Fernando’s memory in our relationship. He’s a part of our love story,” Brent explained. “It’s such an important chapter in Nate’s life. So the idea that we can honor his memory in a beautiful way was exciting to us.”

Nate and Jeremiah By Design premieres Saturday, April 7, airing at 10 p.m. ET the first two weeks and moving to 9 p.m. ET on April 28.