Ariana Greenblatt was only 13 years old when she headed to Budapest, Hungary, during the COVID-19 pandemic to film the sci-fi action comedy Borderland.

At the time, Greenblatt, who plays the lead roles in the film alongside Cate Blanchett, Kevin Hart, Jamie Lee Curtis and Jack Black, was the only child on set for several months at a time – until Hart’s children Heaven (19) and Hendrix (16) came to visit.

“I met her on set because I hadn’t seen kids in four months. It was just straight adults. Then Kevin said, ‘Hey, I’m bringing my daughter. She’s on FaceTime.’ She’s going to hate me for telling this story. So he’s on FaceTime with her. And I said, ‘Oh my God, hey.’ And she started freaking out. I said, ‘Oh my God, you make me feel famous,'” Greenblatt, 16, says in PEOPLE’s August digital cover story.

When they met in person, there was an immediate connection between them.

“We built a bond, painted rocks together and every day they had lunch in my trailer,” she recalls. “It was immediately this crazy bond and connection… they are literally my brother and sister. I love them so much.”

For Hart, too, it was unexpected. “(My kids) were lucky enough to form a bond with the only other kid there,” he says, noting that the trio “ended up spending an incredible amount of time together, staying true to their friendship and building it up. Good people attract good people. I think that’s how they found each other.”

Four years later, Greenblatt is still an honorary member of the Hart family – and she calls the Jumanji: The Next Level Star “Uncle Kev”.

“She’s at my house all the time. This whole ‘Uncle Kev’ thing gets on my nerves, but she doesn’t stop,” jokes Hart, 45.

All jokes aside, Greenblatt knows she’s looking out for him.

“He believes in me so much. Whenever I’m at his house and his friend is there, he says, ‘That’s Ariana. She’s the next big star.’ He just makes me feel really good,” she says.

And he means it: “What I admire most about her is that she is not afraid,” says Hart. “I’m glad we were able to build a bond and become closer, but I’m excited to see what she will bring to the business. And more importantly: Do for the business.”

In BorderlandGreenblatt plays Tiny Tina, a wild teenager on the run through the universe with a penchant for swearing and blowing things up. At the time, she loved the role.

“If the movie had been rated R, which I was promoting, you would hear more of my personality,” she says of the PG-13 film. “I swear a lot. And I give the middle finger too much. I have to stop doing that because I’ve been told to.”

She adds: “While filming, I just felt so free – like I could say and do anything and it would work because Tina is this unpredictable, wild girl.”

Borderland is now in theaters.