Jackie Young always knew he was different to other children growing up, but he could not work out why.

It was not until he got engaged, and had to prove he was Jewish in order get married in a synagogue, that he discovered that he was a Holocaust survivor.

Young was born as Yona Jakob Spiegel in Vienna on 18 December 1941. At the age of nine months, he was deported to Theresienstadt, a concentration camp and ghetto in the Czech Republic. It was dubbed as a “spa-town” in Nazi propaganda, but the on-site crematorium burnt up to 200 bodies a day.

In 1945, the camp was liberated by the Soviet Army, and Young was one of the 300 survivor children flown from Czechoslovakia to Britain after the war. He was one of the so-called “Windermere children” who were taken to safety in the Lake District.

Parts of Young’s childhood are still missing from his memory. To this day at 83, he cannot recollect anything from his early years interned in Theresienstadt, where more than one half of the roughly 140,000 Jews imprisoned were deported for extermination. Likewise, he cannot recall his time in the children’s home Bulldogs Bank in Sussex, where Anna Freud, Sigmund Freud’s psychoanalyst daughter, took a special interest in his upbringing.

Young’s adoptive parents, who first met him at his second care home in Weir Courtney, Surrey, were keen to protect him from the truth. Young did not discover they were not his biological mother and father until a child let it slip at school. Then, as a teen, his adoptive grandmother unexpectedly blurted out that he was Austrian.

“I used to get a lot of information from my dreams,” Young said at his home in north London, sitting on a sofa beside his wife, Lita. “Because I used to dream about my past. I used to ask my mum, ‘Why do I keep dreaming these pointed trees and terraces?’ It was so very vivid. And it turned out it was the second home I went to, Weir Courtney.”

In 1963, when he was about to marry Lita, he uncovered documents about his childhood, setting off a life-long odyssey into his past.

He learnt that he was born at the Rothschild-Spital, a Jewish hospital in Vienna. He suspects his mother, Elsa Spiegel, a Jewish Viennese woman, handed him over to an orphanage before her own deportation in December 1941.

The records indicate that he was either three and a half months old or five and a half months old when he parted with his mother.

While Young was deported to Theresienstadt, his mother was transported to Maly Trostenets near Minsk, where she was shot by Nazis. Young survived in the camp for two years and eight months before it was liberated.

He was the sole survivor out of the 15 other children who travelled with him to the camp. After the end of the war, he was one of the 732 young Holocaust survivors brought to England under a government initiative, commonly known as “The Boys”.

But something was missing from his knowledge about his past – the name of his father, which was omitted from his birth certificate.

At 80 years old, Young still did not know. For most of his life, he feared he might have been the son of a Nazi who protected him.

“Over 100,000 left Theresienstadt to go to Auschwitz and were murdered. Thirty-three thousand died from starvation, suicide and hunger. For a long time, I couldn't understand how I survived, and why only me and not the other children. There was typhoid and typhus. There were so many things that one could succumb to,” he said.

The mystery continued even after Young appeared on a BBC documentary called DNA Family Secrets in 2022.

On the show, geneticist Dr Turi King revealed that Young was 99 per cent Ashkenazi Jewish, so unlikely to be the son of a Nazi, and that he had two second cousins once removed (a brother and sister) on his paternal side.

But the missing piece of the jigsaw – the name of his father – gnawed away.

Luckily, the BBC show caught the attention of two women who had the specialist knowledge needed to solve the 80-year-old mystery.

Jennifer Mendelsohn and Dr Adina Newman are fascinated by DNA –  Jewish DNA in particular.

The two genealogists are behind the Holocaust Reunion Project, an organisation launched in 2024 to empower survivors and their family members to reclaim their history through DNA testing and specialist consultation.

Newman said Ashkenazi Jews were an “endogamous” population. “We descend from a very limited number of people. There's no kind of outside-genetic-anything coming in. It's just those same people having children, over generations. So, you can imagine you're not getting a lot of DNA variation coming into the pool.”

Because Jews share much more DNA with each other than average, tests show a large number of genetic links. “Personally, on Ancestry, I have 200,000 matches,” says Newman. This means untangling Jewish DNA results is notoriously difficult.

To dissect Ashkenazi Jewish genealogy, you also have to be able to translate census and immigration records — often switching between Hebrew, Yiddish, German, Polish and Russian — and understand boundary changes in Europe.

On top of this, there’s the Holocaust. “You're very often chasing ghosts. There are people who disappeared, and you have to figure out what happened to them. For the world's genealogists, it's a given that you can find records on just about everybody. And for us, it's often the exception and not the rule that we will find a record,” says Newman.

Before joining forces to help people like Young uncover their fractured history, the investigative pair felt first-hand the transformative impact of uncovering DNA mysteries in their own families.

Mendelsohn was a journalist, with no particular interest in genealogy until one day in 2013 when she “accidentally fell down the Ancestry hole” and became hooked.

A couple of weeks later, she was in the car with her husband’s grandmother, Frieda, a 95-year-old Holocaust survivor from Poland who had lost her entire family.

Through her own research — “I went on this wild goose chase” — she managed to hunt down three first cousins in two weeks. The process made her realise she had a talent and made her “hungry” for more.

Newman, a professional genealogist and founder of My Family Genie, grew up making family trees but it was not until she started a family of her own that she became obsessed about where she came from, being 99 per cent Jewish and one per cent Scandinavian. She recalls late nights with a newborn in one arm, furiously typing on her computer with the other as she scraped the internet for her origins.

Through her own research with the DNA website 23 and Me, she’s found multiple cousins and uncovered an uncle, previously unknown to the family.

The two women connected over feeling that there was a gap when it came to genealogists having the specialised knowledge required to unravel and piece together the fractured histories of Jews whose lives have been torn apart by the Holocaust.

That’s why in 2022, they launched the DNA Reunion Project, a pilot programme with the Centre for Jewish History, which gave Holocaust survivors and their descendants free DNA kits.

Young was their first case.

Through their specialist work, they managed to uncover the missing piece of the jigsaw which had haunted Young for 80 years — his father’s name: Adolf Kornfein.

Born in 1894, he was a tailor, and was in a relationship with Spiegal following a divorce from his wife, Hilda, with whom he had a child, Wilhelm.

Both Hilda and Wilhelm were deported to Auschwitz on July 17, 1942. Meanwhile, Kornfein was deported with Spiegal to Maly Trostenet, where they were both killed.

As well as the story of Young’s father, Mendelsohn and Newmam’s work uncovered that he had four more living relatives on his paternal side: in Israel, France and the United States.

“It’s very comforting to know that you're not the only one that survived it all, and there is a direct connection,” said Young. “For all my life I thought I was the only one and it's not a good feeling to be alone.”

About the advances in DNA, Young said: “It’s a major door that's opened.” Discovering that he had more living relatives was “mind-blowing”. He’s particularly close to one relative in Missouri and his wife. “They are lovely people. We've done FaceTime, had chats and sent cards and what have you.”

At his home, he’s printed out the family free that Mendelsohn and Newman gave him and framed it on the wall.

“It's gratifying, but it's also always bittersweet,” said Mendelsohn. “You find these things out for these people and it's very reassuring for them, but it's set against this unbelievable backdrop of tragedy and loss.

“I wish Jackie could have had a happy childhood in Vienna with his mother. And instead he has this horrifically tragic story where he was put into a camp as a baby.”

On the 80th anniversary of the liberation of Auschwitz-Birkenau, there is a worry that Newman and Mendelsohn are working against the clock when it comes to reuniting Holocaust survivors with relatives.

“This is at risk history. I always say I wish we'd started yesterday,” says Newman. But on the positive side, “DNA lives forever,” she tells me. “I manage accounts of people who are no longer with us. We've had people in this program who've died after taking it, but their kids can still benefit from the DNA because their DNA can still help solve things.”

That’s why the Holocaust Reunion Project, the independent re-launch of their 2022 pilot with the Jewish Museum, offers free tests to second-generation survivors. “The effect of not having family ripples down from the survivor to their children as well,” said Mendelsohn.

“One of the things that was lost in the Holocaust in addition to the tragic loss of family members was family history,” she said.

“Genocide cuts people off from their family history. You miss the opportunity to sit at grandma's knee and hear the family stories because grandma was murdered.

“So, what we do gives people back their history. Survivors believe they can't build a family tree and that's part of what we do.”

As for Young, it’s “cathartic” being able to visit school children and tell the full story of his once hidden past. He compares the therapeutic process of recounting his traumatic upbringing with an accoholic attending a meeting.

“At one time I couldn't say a word because I got upset,” he said. “But now, by talking about it… I think it has sort of cured me of my fears of the past.”

Newman and Mendelsohn will be presenting a virtual talk with the Association of Jewish Refugees on 13 February. Email nextgens@ajr.org.uk for details.