A Holocaust Survivor Photographed by Kate Middleton Shares How the Pan He Holds in the Photo Saved His Life

A Holocaust survivor who recently sat for a landmark portrait with his two granddaughters was touched by how the photographer, Kate Middleton, took great care to put him and his granddaughters at ease.

The royal mom “was hospitable and interested in our story and my grandchildren,” says Steven Frank, 84, who was invited by Kate to Kensington Palace for the photo shoot to spotlight Frank’s remarkable story and commemorate the 75th anniversary of the end of the Holocaust. Six million Jews were murdered by the Nazis before the 1945 liberation of the most infamous concentration camp, Auschwitz-Birkenau.

Just five years old when the Nazis invaded the Netherlands, Frank was a young eyewitness to the Nazis’ horrific persecution and mass murder of Jews. His father, Leonard, was a lawyer who spoke out against the Nazis and joined the resistance.

“When it became clear the Germans were going to invade Holland, we had ample opportunity to flee to England, but my father was a very humanitarian man and was very much involved with people who were not as fortunate as we were,” Frank tells PEOPLE.

Leonard was betrayed, and in December 1942 he was arrested by the Nazis. Steven and his two brothers, Nick and Carel, never saw him again. He was murdered in the gas chambers on January 21, 1943.

Steven and his mother, Beatrix, and brothers were sent to Westerbork transit camp, then on to Theresienstadt, a hybrid “camp ghetto” in the Czech Republic. Steven and his brothers are three of only 93 children who survived the camp out of 15,000 children sent there.

Kate, who photographed Frank alongside his granddaughters Maggie, 15, and Trixie, 13, “is quite talented. She had a tripod with a Canon camera. She transmitted it to a screen on a monitor, and she would be looking at the monitor at the same time to see if everything was right. She took quite a lot of photographs.” The Duchess also photographed another survivor, Yvonne Bernstein, and her granddaughter Chloe.

“There were minor positional changes, and my elder granddaughter’s hair was a little in the way so was moved to the side. All these minute details which she managed to spot, which makes a good photograph.”

Kate modeled the shoot on a painting by Johannes Vermeer — who was Dutch like the Franks. “It is absolutely beautiful,” he says of the portrait. “She does capture that light that would have been coming through a window.”

Frank and his two granddaughters had each been asked to bring something poignant for the shoot. Maggie had a teddy bear named Abby given to her by her grandparents, while Trixie had a hockey stick, as they knew Kate was an avid player. (“She talked about it with them,” he says.)

Steven Frank brought a pan and a tomato from his garden. The tomato signified the plants he helped another prisoner grow and harvest for food in the last camp the family was kept in, Theresienstadt. “The pan basically kept us alive mainly because of my mother’s incredible versatility at extracting food from here there and everywhere,” he says.

For much more on Kate’s powerful new project, pick up this week’s issue of PEOPLE, on newsstands Friday

The resourceful woman — who died in 2001 at age 90 — got a job in the camp’s hospital laundry. In return for doing washing for other prisoners she was given scraps of bread that she used to make porridge for her children. “Eventually she would get all of these crumbs in a pan, add some hot water and make a paste. She would come into the children’s barracks where I was with my brothers and feed us in turn with one spoon, a mouthful at a time. I never saw her eat a spoonful herself. That food was what kept us going — the pan was the most important thing she took into the camp.”

RELATED: Auschwitz Liberation 75 Years Later: Survivors Reveal How They Cheated Death

He praises his late mother for making sure he and his brothers survived against the odds: “With her motherly instinct and spreading her wings over her three children, we have come out with remarkably little damage.“

He says his mother had an “unbelievable strength of character.” When his father Leonard had been imprisoned because of his work helping other Jews, “she found out who the cleaners were and went in to that prison, disguised as a man — taking this guy’s place and scrubbing the floors — and she briefly spoke to my father.”

In the first camp, Westerbork, where they were taken in March 1943, Frank recalls British fighter jets strafing the camp with bullets because they mistook it for a military camp.

“I had just entered the barrack when the attack began, and I ran through a hail of bullets to our table where we would assemble to eat and talk among the same 10 or so occupants who became our social group,” he says. “I encountered my first death there — a man whom we had come to love, and with whom his wife would reminisce in English with my mother [who was born in Eastbourne, England], a native English speaker, about happy holidays in the U.K. I was deeply shocked to see this wonderful man who loved England so much was killed, riddled by British bullets blood pouring out of his body.”

Later, in Theresienstadt (which he calls Terezin), he and his brothers endured the horrors of witnessing the guards select youngsters to be transported to Auschwitz.

“They split siblings apart, one to go to their certain deaths and one to remain to an uncertain future,” he says. “It’s all that those children had left. One another.

“Parents gone; other sibling disappeared. And I witnessed the howling and screaming as these siblings were torn away from each other. I still hear the pleas: ‘Please let me go with her;’ ‘Let me stay with him.’ To which the guards responded, ‘Nein du raus!’ (‘No, get out!’) pointing their vicious finger to the door.”

RELATED: Prince Charles Delivers Powerful Speech at Israel’s Holocaust Memorial: ‘All Humanity Must Learn’

Today, Steven Frank gives talks in schools and helps keep the history alive. He praises Kate and her husband Prince William who attended a remembrance ceremony in London organized by the Holocaust Memorial Day Trust, for helping to keep the history of the Holocaust in younger generations’ minds.

“Both she and Prince William have been extremely interested in the Holocaust and the Memorial Day. William has been in the press with Holocaust survivors and his father is patron of the Holocaust Memorial Day Trust. There is an interest particularly in letting people know what happened, getting their testimony and passing it along to other generations.”

He appreciates how members of the Royal Family can reach out to other communities through the U.K. and beyond. “The modern ones more so. It started with Princess Diana walking through the minefields.”

“They are genuinely interested in what we are doing and the Holocaust Memorial Trust and what we are trying to do for the younger generation.”