They were identical twins, two black girls in a white world with a bond so fiercely strong, nobody else could get in. Now, their fascinating — and troubling — story is about to hit the big screen.

“It definitely messed with my head,” Letitia Wright told The Post of shooting her new movie “The Silent Twins,” opening in theaters Friday.

When June and Jennifer Gibbons were born, it was clear to their parents early on that something was unique about them. Or, more accurately, between them. 

“They started talking late and when they finally did speak, their words came out garbled. They chirped and squeaked, enunciating the wrong syllables,” Marjorie Wallace, author of the 1986 book “The Silent Twins,” told NPR in 2015. “No one else could understand them. It was like they were speaking a foreign language. They both moved in sort of synchronicity.”

Wright (“Black Panther”) and Tamara Lawrance (“Kindred”) star in “The Silent Twins,” the stranger-than-fiction story of the Gibbons twins; they play a grown June and Jennifer in director Agnieszka Smoczynska’s telling of their perplexing life story, adapted from Wallace’s book.

Jennifer and June’s parents were from Barbados, and the twins were born in 1963 on a British military base in Yemen, where their father was stationed. In the early 1970s, the family settled in Wales, where the girls were the only black children in their elementary school.

The bullying they experienced seemed to increase their bond and unwillingness to communicate with others, earning the girls the nickname “the silent twins.”

“Though the family spoke English at home, young June and Jennifer Gibbons began to speak another language, believed to be a sped-up version of Bajan Creole,” the site All That’s Interesting reported.

As the film shows, June and Jennifer would talk animatedly to each other until another person came into the room, then fall passive and quiet with their heads down.

“Their silence was a protest towards racism — systemic racism that they experienced as children they couldn’t fully understand,” Wright told The Post.

The twins’ bond, though inseparable, was not always a loving one.

According to Wallace’s book, Jennifer once tried to strangle June with the cord of a radio, while June once tried to drown Jennifer after they rivaled for the attention of some boys.

The girls isolated themselves more and more as they got older, receding into their own world, eventually turning to criminal behavior. In 1981, they burned down a tractor dealership, which subsequently caused the injury of a fireman; soon afterward, they were caught vandalizing and trying to set fire to a technical college.

In 1982, the teenaged twins had been arrested and sentenced to Broadmoor, a British maximum-security facility for those pronounced “criminally insane.” In the years leading up to the arrest, they had dropped out of school, holing up in their room to speak in their shared language and to write. They filled countless notebooks with their stories and bought a typewriter so they could submit their work to magazines.

“If they were born in this time, they would be New York Times best-selling authors and prodigies,” Wright said.

The movie brings their fantastical, melancholy writing to life in stop-motion animation sequences.

Wallace heard about the twins from a journalism colleague and began to visit them at Broadmoor.

To her surprise, she forged a friendship with them by telling them their parents had let her read their notebooks. They broke their silence to ask if she liked their writings and told her they dreamed of becoming writers. But the things they had written, she found, included furious screeds about their own relationship. Wallace shared one excerpt from Jennifer with NPR:

“We have become fatal enemies in each other’s eyes,” the twins wrote. “We feel the irritating deadly rays come out of our bodies, stinging each other’s skin. I say to myself, can I get rid of my own shadow — impossible or not possible? Without my shadow, would I die? Without my shadow, would I gain life, be free or left to die?”

Wallace, one of the only people June and Jennifer would talk to, ended up reporting extensively on the behavior that allegedly spooked the Broadmoor staff. The twins would alternate which one of them would eat food while the other one went hungry. For a time they were separated, and staff would discover that both girls, though kept in cells far apart from one another, were motionless, frozen in the exact same position.

Wright said re-enacting the young women’s time at Broadmoor was the most challenging part of the shoot.

“It was really hard for us to do those things every day, but I dedicated myself to it alongside Tamara, because that was the truth of the experience, and I wanted people to see,” she said. “So, yeah, it messed with me, but I gave myself to be a vessel. When you see this film, you will see what they went through.”  

Finally, the twins were eligible for transfer to a different hospital, one that would allow them to be eligible for parole. Before they left, they met with Wallace. Jennifer told her, “Marjorie, I’m going to have to die.” The journalist nervously laughed this off, but the twin insisted, telling her the two of them had made the decision together.

As a bus left Broadmoor with the twins in it, Jennifer reportedly fell onto June’s shoulder, and slipped into a coma. The 29-year-old was declared dead later that day, found to have swelling around her heart.

“The doctors at the Caswell Clinic deduced that the medications given to the girls at Broadmoor must have provoked Jennifer’s immune system — though they also noted that June was given the same medications and was in perfect health upon arriving,” All That’s Interesting reported. 

After her initial shock at Jennifer’s death, June reportedly flourished, coming out of her shell. She is alive today, living in West Wales and is a writer. “The Pepsi-Cola Addict” — a novel she wrote when she and Jennifer were 16 and was initially printed by a vanity press — is due to be published next year.