(CNN)Thomas Edelmann was born in Germany more than 25 years after the Allies defeated Hitler.
Yet last year, following an unexpected marketing call, the 49-year-old businessman contacted a retired teacher in Israel to apologize for the actions of the grandfather he never met.
Growing up, Edelmann had heard rumors about the family business and suspected it had previously been owned by Jews who were forced to sell to his paternal grandfather, Wilhelm.
In recent years, the father of two had begun to dabble in genealogy. He came across Nazi tax records confirming that the Jewish owner -- Benjamin Heidelberger -- was forced to sell the hardware store in Bad Mergentheim, southern Germany, in 1938 following the introduction of the anti-Semitic Nuremberg laws. These laws restricted Jews from the German economy by making it legal to confiscate their property.
Edelmann mentioned this in passing to a salesperson from MyHeritage, the online family tree building site, who had called to discuss his subscription.
Fascinated, the salesman relayed the tale to the company's research team.
Two weeks later, Edelmann received a call from MyHeritage. They had unearthed two important records: Heidelberger's 1942 naturalization record from British Mandatory Palestine, and his gravestone alongside his wife, Emma, in northern Israel. What's more, they had discovered that Heidelberger had a living granddaughter.
Hanna Ehrenreich, an 83-year-old retired teacher, knew all about the store that came to be known as Willi Edelmann. So much so, that a black-and-white picture of it -- bearing the earlier name of her grandfather -- still adorns the walls of her home in Israel.
Edelmann, who had lost touch with his father after his parents divorced in the early 1970s, knew little about his paternal family history and had no connection with the prosperous retail chain that had blossomed from the hardware store.
While the store itself no longer exists, Edelmann's family still owns the building, as well as numerous other properties in the town. He, however, has no stake in the firm.
Edelmann sent a letter to Ehrenreich in English though MyHeritage -- unaware that she actually grew up speaking German.
He wrote: "I believe that if my family supported the injustice your grandparents experienced, it is our duty to take this into account and take over responsibility at least in getting in touch with you to listen and learn. As I am part of the Edelmann family I want to take the first step and listen to you.
"I do understand that you might not see any benefit for yourself personally in talking to me. But with me understanding and being able to teach my children and possibly other family members about the impact of particular historical decisions, this might help them to make better decisions in their lives," Edelmann continued.
"Currently, the political climate in our country is poisoned. There is a new antisemitism upcoming. I want to make sure that at least my family will never again be responsible for injustice experienced by others, but stand up to take part for the weak," he wrote.
After receiving Edelmann's letter, Ehrenreich agreed to talk to him, and weeks later the pair spent 90 minutes discussing their families' pasts on the telephone, in German.