When Fuller House premiered on Netflix nearly three years ago, a whole generation of ’80s and ’90s kids were excited to check back in on the Tanner family. What followed was a fervor of binge-watching, trend pieces, and Michelle Tanner GIFs, but the buzz tempered by the second season. (How rude.) There were still milestones—an Emmy nomination for Outstanding Children’s Program in 2018, for example—but the sitcom mostly settled into a comfortable routine.

By the end of season three, though, that shifted. Fuller House returned to its roots while simultaneously laying the groundwork for its future. Becky, Jesse, and Danny decided to move back to San Francisco so Danny and Becky can host Wake Up, San Francisco again; DJ and Steve reunited; and Fernando bought the Gibbler house. These events allowed the series to keep the family-friendly vibe, while tapping into more modern storylines: namely, the non-nuclear family structure.

Full House (and, as a result, Fuller House) has always been about a non-nuclear family—but it was because of circumstances like the death of Danny’s wife or DJ’s husband, not choice. That’s not the case in season four, which premieres on Netflix today: One of the main storylines will center on Kimmy Gibbler (Andrea Barber) being a surrogate for Stephanie Tanner (Jodie Sweetin).

The seeds for this actually began back in season one, when it was revealed that Stephanie is unable to have children. Then, in season three, she discovered she had a few eggs left but wouldn’t be able to carry a baby. Enter surrogacy as an option. But Stephanie was in a serious relationship with her boyfriend (and Kimmy’s brother), Jimmy Gibbler, and wasn’t sure if she felt comfortable asking him to be the father should one of her eggs be viable. Turns out he was, and by the season’s end an embryo was implanted in Kimmy. Now she’s pregnant—whether it’s a single or multiple birth is TBD.

It’s a sign that Fuller House isn’t stuck in ’90s nostalgia that Stephanie and Jimmy aren’t married or engaged or even concerned about it. They’re just a couple in love who want to have a baby together. Imagine that happening on Full House with Jesse and Becky? For 30-something Stephanie, her biggest priority is starting a family—not worrying about her forever partner.

“It’s definitely not your traditional sitcom storyline of boy meets girl and they have a baby,” Andrea Barber tells Glamour.com. “I think this is more relevant. For a lot of people having a child is not so straightforward—it’s complicated and messy. I’m glad the show went there and didn’t just drop it in season one. It’s been evolving for four seasons.”

The story of Stephanie’s fertility was originally creator and former executive producer Jeff Franklin’s idea. When season one premiered, he told TV Line he wanted one of the three lead women to not have kids—for now. “The backstory I created for her was that she’s a free spirit, traveling the world. She’s into her career and into having fun, and I thought this would be a really interesting aspect to that character—and touching,” he said at the time.

However, executive producer and co-showrunner Steve Baldikoski says that before Franklin departed the series last year he made it known that he wanted season four to be about Kimmy’s surrogacy. “In the last moments of season three, we revealed that Kimmy was pregnant with Stephanie and Jimmy’s baby,” Baldikoski says. “The challenge for [executive producer and co-showrunner] Bryan Behar and I was exactly how that would play out for the year. We wanted to have something that was real and tangible to pull Full House into the modern era of Fuller House.”

So, unlike other sitcoms that have tackled surrogacy (see: Friends, Superstore, The New Normal), the focus will be more on the relationship between Kimmy and Stephanie rather than the baby.

“Kimmy is so happy that she’s finally an important part of Stephanie’s life,” Barber says. “She’s been rejected by Stephanie for many years; now these characters are bonding in a way they’ve never been able to before. Kimmy doesn’t want to let go of that. [She doesn’t want] to feel like an incubator. She wants to feel more important than that, which I think is pretty valid.”

It is valid, given viewers have watched these two evolve from an eccentric 10-year-old and a precocious 5-year-old to the adult women they are today. “They’ve literally watched us grow up on TV,” Barber says. “To watch this fictional character go through such important life moments is incredible and so poignant.” That’s why she wanted the writers to explore Kimmy and Stephanie’s “mature friendship” as a sisterhood. “I’ve just been delighted for the last two seasons to have these wonderful, funny, tender moments with Jodie [Sweetin].”

Of course Full House has always tackled big subjects—DJ’s eating disorder; the death of a close family member—but they were settled in the span of a 22-minute episode. For that reason alone, Baldikoski and Behar wanted to see Stephanie’s fertility storyline through. “Bryan and I like dealing with these real issues over the entire season, not just a single episode,” Baldikoski says. “We like to think that if you’re going through something, it’s best to deal with it in a realistic way and carry it through a season. It’s not just one and done.”

Baldikoski relied on personal stories and research to prep for the storyline. “While Fuller House is not a medical show or a drama, we do have writers who are very familiar with [surrogacy] and had different experiences with that. So we relied on a little bit of that and also sent people off to do research. Without invading anyone’s privacy, there was a lot of sharing about our writer’s experiences and the experiences of friends and friends of friends.”

Barber, a mom of two, hasn’t had personal experience with surrogacy, so she turned to one of her closest friends who did. “Her cousin was her surrogate,” she says, adding that she understands the complexities that come with that. “I would suspect…surrogates don’t want to feel just like baby machines. They want to feel important too.”

As for the birth scene, which will happen toward the end of the season, Barber had a request for the writers: make the labor as realistic as possible. “Sitcoms tend to do really silly births with lots of screaming, and it isn’t like that,” she says. “I wanted there to be an emotional connection, a tender moment between the women. They honored my request—and Jodie’s request—that it just not be a silly birth. There’s silliness trying to get to the hospital, of course, but when it comes to the actual birth scene it’s not gratuitous or over the top. It’s just a wonderful moment, and that’s what I had been hoping for for two seasons. They did it.”

Barber adds that you’ll still see lots of realistic sweat and awkward expressions. “It’s not a flawless, beautiful, ‘my makeup is perfect’ birth. It’s a life-changing moment that we’re all going through, and as realistic as it can be for a sitcom.”

The producers also got the rights to Joni Mitchell’s “The Circle Game” to play over an emotional montage. “I’m choked up as I talk about it,” Baldikoski says. “If it doesn’t make Fuller House fans choke up, I don’t know what will. It’s a beautiful scene. Andrea is amazing, Jodie is amazing, Candace is amazing, Adam [Hagenbuch, “Jimmy”] is amazing. We are very proud of it.”

As to whether the episode will serve as a series finale or season finale, Barber and Baldikoski hope there’s a season five in Fuller House‘s future. After all, there are plenty of stories that can stem from this surrogacy. “Usually surrogates don’t live in the same house as the birth mother,” Barber says. “I would love for them to explore that.” And what effect will this new baby have on Kimmy’s teen daughter, Ramona, and her partner, Fernando? How will Kimmy’s relationship with Stephanie change once the baby arrives? “Those are some pretty rich story areas that we have to deal with going forward,” Baldikoski says.

Whatever happens, Baldikoski hopes this will resonate with viewers. “Families come in all shapes and sizes. You don’t have to be a nuclear family anymore. People can feel comfortable with whatever family situation they have as long as they are loved. We want to show that the Fuller/Tanner clan is very inclusive. We’ve even included the first openly gay teenager on the show [this season], who is a friend of Ramona’s. As DJ says, ‘The door is always open.’ That’s our guiding philosophy of the show: Everyone’s welcome.”

Fuller House season four is now streaming on Netflix.