The trauma of separation from loved ones never goes away, even after almost a lifetime.

Searching for one person in 7 billion is difficult but not impossible.

The blue ink is faded and stretched, but Bodner quietly reads the Auschwitz ID number that will never be erased: A 7733.

Now he is looking for A 7734: The number of his identical twin brother.

KimRon checked the numbers against official Auschwitz records now archived at the Yad Vashem Holocaust Memorial in Jerusalem.

She discovered Bodner was born Eli Gottesman, in Ukraine. He had an identical twin named Jeno, who was last seen by Allied doctors in Auschwitz.

"We know that he was declared healthy on February 9, 1945, by medical staff," KimRon says. "That is really the last factual reference that I have."

KimRon also found other, more disturbing records, showing that the twins were subjected to experiments by Josef Mengele, the Nazi doctor dubbed the "Angel of Death" for his gruesome experiments on humans, particularly twins.

Perhaps thankfully, Bodner has no memory of that.

KimRon has not ventured further into the Nazi historical archives in Berlin to find out more about what happened to Bodner in the camp, and he insists he does not want to know -- but he does want to trace his brother.

Now, the pair have turned to social media for help, setting up a Facebook page, A 7734, which has been viewed more than a million times.

Each time the page is shared, KimRon hopes it brings them one step closer to finding Jeno. Several nurses have contacted her after seeing what might be the matching tattoo.

"It's like a thread," KimRon explains. "There's three types: One that leads to nowhere. One you think will go somewhere, and you reach a deadlock. And then there's one that takes you to your destination."

CNN has a video: