Warsaw, Poland(CNN) Jan Gebert handed his apartment keys to the family he had just met. The Ukrainian mother wanted to pay. No, insisted Gebert, this is free.
It was days after Russia invaded Ukraine and one of the countless acts of kindness being shown to those fleeing danger and reaching safety in Poland. But for Gebert, 42, it was very, very personal.
"My family survived the war because someone helped them. They were refugees. That's the reason why I'm here," he said. "Thanks to that time, I can help other people."
Gebert is descended from Holocaust survivors, some of the few who lived through Hitler's obliteration of Warsaw's Jewish community, which was then the largest in Europe.
To not help others now is unthinkable to him, so he and his girlfriend repeatedly invite refugees to stay until they have somewhere more permanent. As a third family arrives, Gebert and his girlfriend inflate a mattress for themselves and give the bedroom of their 400-square-foot Warsaw apartment to their new guests.
"It is not a big apartment," he told them, apologetically, though the refugees replied it was just the shelter they needed from the war.
Gebert said he hoped the woman from Kyiv and her young son would finally be able to rest.
"Everything which I own and have in my life is in this apartment," Gebert told CNN. "I don't know if it's faith or tradition. But I have to."
A few city blocks from Gebert's home is the site of the Warsaw Ghetto, where Nazis first imprisoned Jews behind a high wall topped with barbed wire and then deported them to death camps during World War II.
Almost daily, he walks past the building where his great-grandmother, Zofia Poznańska, lived before the war. He has a few photographs of her -- as a toddler with a large bow holding back curly tendrils from her wide eyes; as a girl; a teenager, and finally as a mother with her own daughter, who would become Gebert's grandmother.
With the Nazis in charge of the city, Zofia became separated from her husband Julian Poznański and Krystyna, their daughter. Krystyna was evacuated to Siberia, Gebert said. His great-grandfather was taken in and hidden by non-Jews in Poland. But Zofia was falsely told both were dead and, overcome with grief and believing she had nothing to live for, she handed herself to the Nazis, according to Gebert family history.
That's the last they ever heard of her for certain, Gebert said. They believe she was taken to the Nazis' Treblinka death camp, northeast of Warsaw, where she died, though the exact details, like the fates of many of the more than six million Jews murdered in the war, were never unearthed by the generations who followed.
One great-grandparent was sheltered and survived. One had no help and died.
That reality was always in Gebert's mind when the refugees from neighboring Ukraine started to flood into Poland.
"My entire family is involved in helping refugees," Gebert explained. His father has given up his apartment. His sisters have ferried Ukrainians from the Polish border into Warsaw. "We are living because my ancestors were in hiding in Poland," said Gebert.
And this time, unlike in the 1940s, there are many in Poland willing to help when the need is so clear, even though the country has resisted waves of recent exiles from Middle Eastern countries like Syria.
Poland's Chief Rabbi Michael Schudrich told CNN there was no comparison between the bravery of those who sheltered Jews against the Nazis and civilians supported by their government opening their doors to help Ukrainians. But it was still doing what needed to be done.
"We're doing nothing compared to what these truly righteous people did during the war," he said.
"It's our time to do what we needed to have done for us 80 years ago ... If we still have, somewhere in our hearts, a sadness that more people didn't help, it needs then to push us to do more to help now, rather than becoming angry or turning inwards, it needs to motivate us to even do more."
Most Polish Jews who survived the Holocaust left the country after the war. Today, there are fewer than 10,000 Jews in Poland, according to the World Jewish Congress. Schudrich said the Ukrainian refugee crisis hit home differently to members of the Jewish diaspora, including those of Polish origin, because of that history in addition to the Jewish tenet of helping those in need at any cost. He said global Jewish philanthropies, mainly in the US, have raised about $100 million to help Ukrainian refugees.
Even though he is surrounded by his family's sometimes painful history, Gebert says he tries not to dwell on the past. But asked what life could have been like if more of his relatives had been saved from the Nazis, he sounds almost wistful.
"If someone had helped those, my ancestors, my cousins, during the Holocaust, I will have much greater family next to me," he said.
"That would be wonderful -- to have a great big family in Warsaw, a Jewish family which survived the war, that would be the most beautiful, beautiful thing."
CORRECTION: An earlier version of this story misspelled Jan Gebert's last name.