"My grandfather never talked about the Holocaust or what he had escaped," he said.
Mr Nicholls, from Wallington, near Croydon, was one of 65 regional ambassadors taken by the Holocaust Educational Trust to visit Yad Vashem this summer.
He said: "I did the Lessons From Auschwitz project with HET two years ago and I was a little bit aware of my grandfather's family and how they had fled the Nazis.
"He was a Dutch Jew and fled from Rotterdam in sailing boats the day the Germans invaded in March 1940.
"His extended family stayed behind and they didn't survive. But I had no idea how many had died."
The 10-day trip is designed to equip the ambassadors with enough knowledge to share with their peers.
Mr Nicholls who is studying military history at the University of Kent, used his spare time to research his family history.
He said: "I knew about 15 or so had died in Auschwitz but as I started looking into it more I discovered over 150 names.
"I wasn't aware there were so many. I kept uncovering more and more names."
He was helped by other members of the study trip.
"I was overwhelmed by the kindness. They suggested I go to the hall of names to research and because we had so many names everyone came to help. It was really touching.
He added: "I wasn't sure how to feel at the time, I was so preoccupied with the sheer volume of names. "It only started to hit me a week ago when I made my way through the list and I found two babies, one eight months old, the other only three-months."
Mr Nicholls said he had visited Auschwitz two years ago as part of an HET group, but it wasn't until the discovery in Israel, that he understood the true impact of the Holocaust.
"To think that 95 per cent of those 150 people died in a place I had visited is a weird feeling.
"I think I'd have been a lot more emotional at the time if I had known. I walked on the exact spot they did before they died."
Mr Nicholls is now compiling testimony on the lives of his murdered relatives to place at Yad Vashem.
He said: "Most of them were just part of a list of murdered Jews from the Netherlands.
"I want to make sure they are not forgotten."
He is also planning to set up a Holocaust commemoration and remembrance society at his university.
"The trip made me think about the Holocaust in different ways.
"And I want to be able to remember and honour those who lost their lives more than anything else."
The Holocaust Educational Trust’s Appeal Dinner is taking place on Wednesday 14th September. To find out more about the work of the Trust, please visit www.het.org.uk
