Now, Priska, Rachel and Anka's story has been told in a new book by journalist Wendy Holden. They respectively gave birth to Hana, Mark and Eva - the "miracle babies" and believed to be the youngest survivors of the Holocaust. The three babies, now grandparents, were born within weeks of each other and yet they met only five years ago.
The launch of Born Survivors in Mauthausen this month on the 70th anniversary of the liberation, was "emotional" for Holden. She says that watching the "babies" stand beside international dignitaries at the event "was incredible. I could not help but imagine, 'what would Hitler have thought?'"
Holden has spent the past 18 months researching the mothers' stories. During that time, she has visited the graves of all three. She says: "It was very important to me that I did that. I collected stones from my beach in Suffolk and I took them there. I cried every time.
"When I went to the mothers' graves I did say one thing to each of them. I asked the mothers for their blessing to tell their stories. These were three remarkable women - and this is a remarkable story. I have not stopped crying throughout writing this book. What saved it for me, weeping as I wrote, was knowing that there was a happy ending. This was a story of courage and defiance.
"All the mothers and babies would say it was luck that they were not singled out by the SS guards, luck they were not tripped up on the march, luck that they didn't cut or hurt themselves and get something that could have killed them. They would say it was luck that they were given huge baggy clothing to cover themselves.
"I am very interested in war and history yet nothing has ever been written about the babies who were born in the Holocaust. I consider them to be the voices of the voiceless - they were exceptional women for their era.
"What I did not expect was how close I would become to the babies and how close they would become themselves. They have called themselves siblings of the heart and I am the honorary sibling."
Mark, who was born in an open wagon en route to Mauthausen, says it was a "huge surprise" to discover others had survived similar circumstances.
He says: "We never knew that there were other babies that had survived such circumstances.
"My mother would talk about her experiences in the concentration camp and she would start crying. The hardest part for her was talking about her brothers and sisters who did not survive. She was one of nine, and five survived. The five were old enough to be of an age where they were strong enough to work.
"For me, this is not a story about survival over adversity - it was just that we managed to survive. But my mother did not give herself enough credit. Even after the war, she never dwelt on how bad her knees were, or having open-heart surgery; she was always saying that others had it worse.
"If anyone suggested that she survived the war and was able to bring out a baby alive because she was strong, she would say that the difference between the people who survived the war and the people who died, was luck. A big part in her thinking was that my natural father was the strongest person she knew. She just thought if anyone could have survived the Holocaust, it would have been him."
Sadly, however none of the fathers survived - and the mothers had no other children.
As for going back to Europe, Mark says: "It is still difficult when I get to Mauthausen, or any of the specific sites where bad things happened. I can picture the people who would have been part of my world and family if it were not for what had happened."
Mark, a doctor, grew up in Munich before moving to Israel, and then America. But ask the German speaker if he considers himself to be German, and he answers: "No. I am as far from being a German as possible. When I was 10, they asked me what I wanted to be. I said I wanted to be a soldier so I could kill as many Germans as possible.
''As soon as my mother got a sense that I was growing up with a visceral hatred of Germans, she spent a lot of time talking me down. Her big message was: if you turn into a person who wants revenge, then they have taken your soul. It took me a long time to accept that.
"The first I learnt of my mother's story, was that I was born on a train. I did not recognise that as being too horrible. But I had no idea how horrendous the situation was. I did not picture it until I had to deliver a baby - it was difficult to think about she went through," he says, regretting that Mengele was never captured like Adolf Eichmann.
"When I think about what Mengele did, I have to consciously drive it away from my mind. "
Eva has committed to telling her story in schools across the globe in a bid to boost Holocaust education. She says: "None of us had another sibling and the coincidence with our stories are just so remarkable. My mother was always able to talk about what happened to her. I knew all about it from a very young age, I was like a sponge - always asking questions.
"I think being pregnant had a lot to do with my mother's survival. She always felt she would survive despite being surrounded by death. A lot of people committed suicide after the war, but I gave her something to live for. She had no family but she had me, and had to get on with it."
During her speaking engagements, she has had a couple of hostile experiences. She recalls: "On the whole, people want to hear my mother's story. People can identify with one family's story - they cannot identify with six million.
"But I once spoke at the history society in Oxford University, and one man said there were no gas chambers outside of Poland. I said: 'Yes there were, I was almost killed in one'.
"At another school, a sixth-former would not hear me speak. His family were members of a far-right group.
"I just take it on the chin and carry on. My mother would sometimes get upset while we watched the news. She asked if I was making a difference. I said, 'that is not a reason not to try'."
Hana, the third miracle baby, hopes readers take the book's strong messages: "We all must remember the horrors of hatred against a difference of beliefs, and that it is possible to survive even the worst… The most important message I got was to not squander my opportunities in life, as I must prove myself worthy of survival."
Working on the book with Holden was "emotional… my mother has not portrayed herself as a victim, but as a survivor."
She continues: "My mother spoke occasionally about her experiences: hunger, cold, fear, beating. She spoke about her older sister and parents, and her young husband, my father.
"The two things that kept my mother alive was the wish to be a mother and to see her love, my father again. The latter, alas, did not happen."
