Rainer Hoess was 12 years old when he found out his grandfather was one of the worst mass murderers in history.

The gardener at his boarding school, an Auschwitz survivor, beat him black and blue after hearing he was the grandson of Rudolf Hoess, commandant of the death camp synonymous with the Holocaust.

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"He beat me, because he projected on me all the horror he went through," Rainer Hoess said, with a shrug and a helpless smile. "Once a Hoess, always a Hoess. Whether you're the grandfather or the grandson – guilty is guilty."

Germans have for decades confronted the Nazi era head-on, paying billions in compensation, meticulously teaching Third Reich history in school, and building memorials to victims.

The conviction Thursday in Munich of retired Ohio autoworker John Demjanjuk on charges he was a guard at the Sobibor Nazi death camp drives home how the Holocaust is still very much at the forefront of the German psyche.

But most Germans have skirted their own possible family involvement in Nazi atrocities. Now, more than 65 years after the end of Hitler's regime, an increasing number of Germans are trying to pierce the family secrets.

Some, like Hoess, have launched an obsessive solitary search. Others seek help from seminars and workshops that have sprung up across Germany to provide research guidance and psychological support.

"From the outside, the third generation has had it all – prosperity, access to education, peace and stability," said Sabine Bode, who has written books on how the Holocaust weighs on German families today. "Yet they grew up with a lot of unspoken secrets, felt the silent burdens in their families that were often paired with a lack of emotional warmth and vague anxieties."

Like others, Hoess had to overcome fierce resistance within his own family, who preferred that he "not poke around in the past." Undeterred, he spent lonely hours at archives and on the Internet researching his grandfather.

Rudolf Hoess was in charge of Auschwitz from May 1940 to November 1943. He came back to Auschwitz for a short stint in 1944, to oversee the murder of some 400,000 Hungarian Jews in the camp's gas chambers within less than two months.

The commandant lived in a luxurious mansion at Auschwitz with his wife and five children – among them Hans-Rudolf, the father of Rainer. Only 150 meters away the crematories' chimneys were blowing out the ashes of the dead day and night.

After the war, Hoess went into hiding on a farm in northern Germany; he was eventually captured and hanged in 1947, in front of his former home on the grounds of Auschwitz.

"When I investigate and read about my grandfather's crimes, it tears me apart every single time," Hoess said during a recent interview at his home in a little Black Forest village.

As a young man, he said, he tried twice to kill himself. He has suffered three heart attacks in recent years as well as asthma, which he says gets worse when he digs into his family's Nazi past.

Today, Hoess says, he no longer feels guilty, but the burden of the past weighs on him at all times.

"My grandfather was a mass murderer – something that I can only be ashamed and sad about," said the 45-year-old chef and father of two boys and two girls.

"However, I do not want to close my eyes and pretend nothing ever happened, like the rest of my family still does....I want to stop the curse that's been haunting my family ever since, for the sake of myself and that of my own children."

Hoess is no longer in contact with his father, brother, aunts and cousins, who all call him a traitor. Strangers often look at him with distrust when he tells them about his grandfather – "as if I could have inherited his evil."

Most dreaded torturer at Auschwitz

Despite such reactions, descendants of Nazis – from high-ranking officials to lowly foot soldiers – are increasingly trying to find out what their families did between 1933 to 1945.

"The Nazis – the first generation – were too ashamed to talk about the crimes they committed and covered everything up. The second generation often had trouble personally confronting their Nazi parents. So now it is up to the grandchildren to lift the curses off their families," said Bode.

It was only during her university years – reading books about the Holocaust – that Ursula Boger found out her grandfather was the most dreaded torturer at Auschwitz.

"I felt numb for days after I read about what he did," recalled Boger, a shy, soft-spoken woman who lives near Freiburg in southwestern Germany. "For many years I was ashamed to tell anybody about him, but then I realized that my own silence was eating me up from inside."

Her grandfather, Wilhelm Boger, invented the so-called Boger swing at Auschwitz - an iron bar that hung on chains from the ceiling. Boger would force naked inmates to bend over the bar and beat their genitals until they fainted or died.

Boger, 41, said it took her several years of therapy and group seminars to begin to come to terms with the fact her grandfather was a monster.

"I felt guilty, even though I hadn't committed a crime myself, felt like I had to do only good things at all times to make up for his evil," she said.

Like Hoess, Boger never personally met her grandfather, who died in prison in 1977. After her father died five years ago, she found old letters from her grandfather begging to see his grandchildren in prison – something that never happened.

"It all just doesn't go together," Boger said. "He is the man who killed a little boy with an apple who came in on a transport to Auschwitz, by smashing his head against a wall until he was dead, and then picked up and ate that apple.

"At the same time, he put a picture of myself as a little girl over his bed in prison. How am I supposed to come to terms with this?"

Tanja Hetzer, a therapist in Berlin, helps clients dealing with issues related to their family's Nazi past. While there are no studies or statistics, she said, many cases indicate that descendants of families who have never dealt with their Nazi family history suffer more from depression, burnout and addiction, in particular alcoholism.

In one prominent case, Bettina Goering, the grandniece of Hermann Goering, one of the country's leading Nazis and the head of the Luftwaffe air force, said in an Israeli TV documentary that she decided to be sterilized at age 30 "because I was afraid to bear another such monster."

Some grandchildren of Nazis find a measure of catharsis in confronting the past.

Alexandra Senfft is the granddaughter of Hanns Elard Ludin, Hitler's Slovakia envoy who was involved in the deportation of almost 70,000 Jews. After Ludin was hanged in 1947, his widow raised the children in the belief their father was "a good Nazi."

In her book, "The Pain of Silence," Senfft describes how a web of lies burdened her family over decades, especially her mother, who was 14 years old when her beloved father was hanged.

"It was unbearable at times to work on this book, it brought up fears and pain, but at the same time I got a lot out of writing it all down," Senfft, a lively 49-year-old, explained during an interview at a Berlin coffee shop.

"If I had continued to remain oblivious and silent about my grandfather's crimes, I would have become complicit myself, perhaps without even being aware of it."

Senfft said she also wrote the book so her children could be free of guilt and shame, and that confronting family pasts is essential for the health of German society as a whole so that history does not repeat itself.

These days Rainer Hoess lectures schoolchildren about the Nazi era and anti-Semitism. A few months ago, he visited Auschwitz for the first time and met a group of Israeli students.

That day was "probably the most difficult and intense day in my life," Hoess said, but it was also liberating because he realized that the third generation of Jews after the Holocaust did not hold him responsible. One Israeli girl even gave him a little shell with a blue Star of David painted on it, which he now wears around his neck on a black leather necklace at all times.

Hoess was embroiled in controversy in 2009 when Israeli media reported he tried to sell some of his grandfather's possessions to Yad Vashem, the Israeli Holocaust Memorial. But email correspondence seen by the AP backs up Hoess' assertion that he would have been just as willing to donate the items.

Hoess eventually donated everything he owned from his grandfather – including a trunk, letters and a cigar cutter – to the Institute of Contemporary History in Munich.

Hoess acknowledges that his grandfather will probably never stop haunting him. After his visit to Auschwitz, he met Josef Pacynski, a Polish camp survivor and the former barber of Commandant Hoess.

"Somehow, subconsciously, I was hoping that maybe he would tell me one positive story about my grandfather, something that shows that he wasn't all evil after all, that there was some goodness in him," Hoess confided.

Pacynski asked Hoess to get up and walk across the room – then told him: "You look exactly like your grandfather."