On a recent summer evening, identical twin sisters Brittany and Briana Deane Salyers had a realization as they drove up the road leading to the Virginia manor they share with their identical twin husbands and two young sons: "We did it!"

Approaching the father-son pairs waiting for them on the porch, Brittany and Briana "held hands for a second," Briana tells PEOPLE. "We were like, 'Oh my gosh, our dream has come true. How lucky we are that we get to live it.'"

For the 35-year-old sisters, who had always wanted to marry identical twins and share their lives together, the journey to this heart-warming moment has been better than they could have imagined.

Brittany and Briana first met Josh and Jeremy Salyers, now 38, at the 2017 Twins Day Festival in Twinsburg, Ohio, where they returned a year later to marry in a joint ceremony. They went on to welcome sons Jett (born to Brittany and Josh, who announced the birth in January 2021) and Jax (born to Briana and Jeremy approximately four months later). The children are cousins but also genetic siblings known as "quaternary twins."

As the parents prepare to take Jett, now about 21 months, and Jax, approximately 17 months, to the festival this year, they're opening up to PEOPLE about their "quaternary marriage," sweet rainbow babies, whimsical wedding venue (which doubles as their home!) and more.

A 'Magical Existence' in the Countryside

Early last year, the couples bought a mansion near picturesque Smith Mountain Lake in central Virginia, named the expansive country estate Smith Mountain Manor and transformed it into a wedding venue. The grounds include a pool, vegetable gardens and acres of lawns. Inside, Josh and Jeremy built a nursery for Josh and Jax, who are being raised as brothers.

"We do everything as a family, we're really inseparable," says Briana. "It's like this magical existence."

A half-century ago, psychiatrist Robert Ravioli even coined a term for the rare instances of identical twins marrying identical twins: the "quaternary marriage," which he lauded for its significant emotional and economic advantages.

The family is now setting a modern-day example in their living quarters in the mansion, where they share all the rooms — with one exception.

"Each couple has their own bedroom," says Briana. "We do like to make that clear because we get a lot of weird creepers."

The two dads, who primarily run the Smith Mountain Manor weddings, take over parenting duties when Brittany and Briana, both attorneys, head off to work at the same law firm four days a week. Once the four adults are home, they all take part in raising the boys, as well as grocery shopping and cooking their shared, primarily plant-based meals.

'Two Dadas' and 'Two Mamas'

Jett and Jax are bonded to all four adults, whom they manage to tell apart despite the striking resemblances. "Sometimes they both want one mom, or they'll turn around and both want the other mom," says Briana.

The ever-smiley Jett recently looked back and forth at Josh and Jeremy and called them "two dadas," and similarly called Brittany and Briana "two mamas" — a moment the family shared with their 210,000 Instagram followers.

"When you realize your parents are ALL identical twins!" the parents, who share the @salyerstwins Instagram page, wrote in the video caption.

"Jett laughs and it's like he gets it," Brittany says of their family structure.

Finding Work-Life Balance

Since purchasing the property in February 2021, Josh and Jeremy have been busy working on renovations, while the attorney sisters have a creative side project: jointly writing a historical novel involving, of course, identical twins. The book is due in December.

The couples also prioritize dates on the property, stealing away to the pool, the gardens, the theater and library — "just some different places that you can be alone," says Brittany.

"We always say the manor has all the rooms from the game Clue," she adds. "When we're done having our own little adventures, we get back and all four of us are with the kids."

Jett and Jax, meanwhile, love to be outdoors, especially for rides in their double stroller and play time. They get along well "most of the time," says Jeremy, laughing. "They give each other kisses."

Making Their Dreams Reality

Briana and Brittany, who love dressing the same unless it's laundry day, had long envisioned their life like this, but they were still looking for partners when they attended the twins festival five years ago at 30 years old. Now they're set to return to Twinsburg for this year's event, from Aug. 5 to 7, alongside their husbands and children — a full-circle moment.

The ladies remember spotting the Josh and Jeremy from afar in 2017 and then meeting them by chance on the last day. Sparks immediately flew, with Jeremy and Briana hitting it off while Brittany and Josh chatted away.

"My reaction was like, 'Oh my gosh, we feel so drawn to them — I hope they feel like that about us too,'" says Brittany. "We found out later that they went home after meeting us and they told their mom that they were going to marry us."

Josh and Jeremy made frequent seven-hour car trips from their home in Tennessee to see Briana and Brittany in Virginia, and within months, the brothers made a surprise joint proposal at Twin Lakes, Virginia.

"It was an incredible joy for me and my husband to see our daughters and Josh and Jeremy fall in love," adds their mom, Debra Deane.

"Marrying twins is something Brittany and Briana had wanted since they were little girls, and I had begun to worry it might not happen," Debra continues. "Because what are the odds, really? It was wonderful for all of us when it finally happened."

Supporting Each Other Following Devastating Miscarriages

After the joint wedding on Aug. 4, 2018, the couples spent the next two years living in the same house in a town about an hour outside of Richmond, Virginia. During that time, Briana and Brittany each suffered a miscarriage early in their pregnancies.

"There was a lot of stress that went along with the timing and the dream of having overlapping pregnancies and then the miscarriages," says Briana. "It was very hard, and it was something that we were all going through. It was devastating on all four parents."

Welcoming Double Rainbow Babies

Brittany became pregnant with Jett mere weeks after her miscarriage, while Briana became pregnant with Jax a few months after hers.

"It was a double tragedy followed by a double joy," Briana says. "Actually, right before we found out that I was pregnant with Jax, we saw a double rainbow over Smith Mountain."

"It was this magical moment," she continues, "because we already knew Brittany was pregnant with a rainbow baby. We were very much stressing about hoping for a second miracle to happen with me, and it did."

Ultimately, the experience was a reminder that having three best friends to lean on at all times makes "life's trials less lonely and brighter," says Brittany.

As for more kids? "We are still debating," says Brittany. "We would be very happy if we just have our two boys. We feel very fulfilled, but we're also open to another pregnancy each."

When that time comes, "it's definitely a group decision," says Josh. "It would never be just one couple saying, 'Yeah, okay. We're going to try now.' It would just never happen like that."

Sharing 'Togetherness'

The foursome was featured in season 1 of TLC's Extreme Sisters and recently agreed to a new TV project, which, as of publication, is still being finalized. By opening up about their lives, they hope to shine a light on the blessings of family.

"Identical twins, in particular, come into this world never knowing what it was like to be alone," says Briana. "Our more natural state is the togetherness, and that helps us."

Adds Brittany: "As far as our setup with being in a 'quaternary marriage' — identical twins married to identical twins, and we're all living together — of course not everyone is a twin, but having family members who can support you and who you can support, it goes a really long way."