Conjoined Twins Who Made Headlines for 2002 Separation Surgery Turn 21: Inside Their Lives Now

Josie Hull and her twin sister Teresa Cajas were not expected to live past their first birthday. In July, the sisters turned 21.

"In the eyes of the world they're both deemed challenged, but they've touched so many lives," Josie's mom, Jenny Hull, tells PEOPLE in this week's exclusive story. "This birthday is such a huge milestone to celebrate."

Today, the girls' bond is stronger than ever. Of Teresa, says Josie, "I adore her. She can't walk or talk, but I can understand her and she can understand me. We communicate through our eyes."

Born joined at the head in a remote Guatemalan village in July 2001, the girls traveled to Los Angeles in August 2002, where a team of surgeons in managed to successfully separate them after a grueling 23-hour procedure that made international headlines.

"It was very risky," says Dr. Mark Urata, head of plastic and reconstructive surgery at Children's Hospital Los Angeles, who was involved in the procedure. "At the time, the success rates for similar separations were not great."

Conjoined Twins rollout
Conjoined Twins rollout

Yuri Hasegawa Josie Hull (right) and her twin sister Teresa Cajas in July.

But the twins soon faced another challenge. After returning to Guatemala, they contracted life-threatening brain infections. Teresa soon required round-the-clock care back in Los Angeles as Josie battled seizures and other medical complications.

With every setback, the twins' will to survive grew stronger, and their parents soon made the excruciating decision to allow their daughters' American hosts to adopt them. "We talk every Sunday," Josie says of remaining close with her birth parents. "They're really proud of both of us."

Conjoined Twins rollout
Conjoined Twins rollout

Amy Waddell/ UCLA Childrens Hospital/Getty Josie (on right) and Teresa in 2002, just months before their separation.

For much more on Teresa and Josie's amazing journey, pick up this week's issue of PEOPLE, available on newsstands Friday

Now the sisters — who both graduated high school (Teresa attended a special education program) in 2020 — are leading lives few imagined possible, including serving as the inspiration for Once Upon A Room, a nonprofit that provides personalized hospital room makeovers for children fighting serious illnesses.

Conjoined Twins rollout
Conjoined Twins rollout

Yuri Hasegawa From left: Josie, mom Jenny, Teresa's mom Florie and Teresa's brother Werner at the twins' 21st birthday party.

Looking back on their incredible journey, Josie, who lives 30 minutes away from her sister in the Los Angeles area, says she still struggles to comprehend their early ordeal. "I don't remember too much because I was so little," she says. "But I love hearing the stories from my mom — it's all pretty shocking to me."

RELATED: Formerly Conjoined Twin Gives Birth to Daughter at Hospital Where She Was Separated from Sister

Teresa's mom, Florie Cajas — along with her husband, Werner — marvels at the sisters' remarkable connection: "Josie can always get smiles out of Teresa that other people can't."

Even the physicians who have worked with the twins over the years are amazed at their grit. "None of this would have been possible without the care and love that their families have put in over all these years to maximize their potential," says Dr. Robert Kay, chief of orthopedic surgery at Children's Hospital Los Angeles.

Conjoined Twins rollout
Conjoined Twins rollout

Yuri Hasegawa Teresa (left) and Josie in July.

These days, Josie's life involves flying around the country and decorating pediatric hospital rooms with her nonprofit. "That's really important to me," says Josie, adding, "Just be happy. And just keep moving on and moving forward."