Are Helen Mirren and Harrison Ford secretly related? The actress seems to think it could be a possibility.

The legendary actors play onscreen couple Cara and Jacob Dutton in the Yellowstone prequel series 1923, and the way that they’ve clicked on camera and off makes Mirren, 79, think they ought to look into just how “connected” they are.

“Harrison and I have a weird thing,” Mirren tells PEOPLE as she explains that despite not working together since The Mosquito Coast in 1986 prior to reuniting for1923, the actors always had what she compares to the relationship with “your best friend in college that you haven’t seen for like 30 years, but [once] you’re back, [it’s] exactly [the same], only even better, actually. Even better.”

“I don’t know if you feel the same, Harrison, but I certainly feel like that, that there is this weird, connected[ness],” she says, before offering up an idea that shocks him.

“Maybe we should do a DNA [test]. Maybe we are brother and sister in the end or something like that.”

“Well, that makes it even more bizarre,” Ford, 82, says candidly, prompting his costar to amend her original statement. “Maybe cousins. That would be better.”

For his part, Ford says that the “main attraction” of 1923 for him “was a chance to work with her again,” to which she agrees.

“The reality is that we met 40 or 50 years ago when we were doing Mosquito Coast. And so we meet now 40 years later. I’ve been told that she’s already signed up. She’s been told I’m already signed up,” he says.

“But somehow, we find ourselves here. And there are 1,000,000 different kinds of actors. They’re [as] different as dentists are to one another — but when there’s a fit, you feel it,” he continues of his and Mirren’s onscreen chemistry. “It’s just a perfect bit of casting.”

In 1923, the actors tell what Mirren described as a “rare” love story, as it’s not the relationship stage that’s typically shown onscreen.

“In movies, people get married or they meet-cute and they fall in love and they have hot sex or whatever, and then it’s all over, happily ever after. Well, this is the ever after,” she said.

“Now we’re seeing what happens at the end of that story, and you very rarely see that onscreen, but it’s actually something that people love to see.”

Ford agrees, saying, “These two are partners as much as lovers, and depend on each other for things that are not part of their quiver of arrows. And it’s an extraordinary relationship that Taylor [Sheridan] has written for us to inhabit.”