When Jared Kushner was 17 years old, he stood where 1 million Jews had been murdered and listened to Israel’s prime minister stress the country’s importance.

“The Holocaust could have been prevented. We know it could not have taken place had the Jewish state been established a few years earlier,’’ the prime minister, Benjamin Netanyahu, said in 1998, standing amid the ruins of an Auschwitz-Birkenau crematory.

Netanyahu had just led Kushner and thousands of other teenagers waving Israeli flags in a procession through the camp’s gates and past the barracks. As part of the commemoration, the group would soon leave Poland and fly to Israel, to complete the journey from slaughter to Zionist rebirth.

Back then, Kushner was a high school basketball player, a Billy Joel fan, a quiz team manager, and no one’s guess to become a negotiating partner with Netanyahu. But unlike other students on the trip, he knew the prime minister, who was friendly with his father, a real estate developer and donor to Israeli causes. Netanyahu had even stayed at the Kushners’ home in New Jersey.

On Wednesday, when the Israeli prime minister visits the White House, Netanyahu and Kushner will reunite on far different terms from before — and yet their meeting will be imbued with some of the shared ideas of those old encounters. Netanyahu is on his second stint as prime minister; Kushner, now 36, is President Donald Trump’s son-in-law and a leading adviser on Middle Eastern affairs with a formidable assignment. Trump has said that Kushner will try to “do peace,’’ which the president has called “the ultimate deal.’’

Kushner has been speaking with Arab leaders in recent weeks. But he is a mystery to most Middle Eastern officials. He has no experience in government or international affairs. His up-close exposure to the ­Arab world amounts to trips to a handful of Persian Gulf countries and one jaunt to Jordan.

Even though Kushner has visited Israel since childhood, and more recently to do business, he is little known there. Though he holds strong views about the state of Israel, he has not been outspoken about them, save for editorials in The New York Observer, the newspaper he owns. His thinking on sensitive matters like settlements is not well understood.

“Israel wasn’t a political discussion for him; it was his family, his life, his people,’’ said Hirschy Zarchi, rabbi at the Chabad House at Harvard, where Kushner was an undergraduate.

Kushner has ties to Israel that are personal and religious. His grandmother survived the Holocaust by crawling through a homemade tunnel in Poland. His grandfather escaped the massacres by hiding in a hole for years. An Orthodox Jew, Kushner, who was educated at Jewish schools, was instructed to protect Israel, remember the genocide, and assure the survival of the Jewish people, those close to him say.

His family used its real estate fortune to donate millions of dollars to American Jewish and Israeli hospitals, schools, and other institutions, including a few in settlements, according to public records. In his classes, Palestinians were regarded at a distance, in part as security threats who committed acts of terrorism — including one that killed a sister of a classmate.

When Trump ran for president, his son-in-law’s stances on Israel helped shape the campaign. Kushner helped script a speech to the American Israel Public Affairs Committee and consulted with Netanyahu officials behind the scenes. When he brought the candidate and the prime minister together for a meeting, he invited his father, Charles Kushner, to join them.

Thanks in part to Jared Kushner, Netanyahu will arrive at a White House that has adopted many of the prime minister’s perspectives on the region. Mustafa Barghouti, a Palestinian leader who was involved in peace talks with Israelis and internally, said Palestinians were skeptical of Kushner, and Trump’s team generally, seeing them as close only to the Israeli side.

“We need somebody who is really impartial,’’ Bargouti said, pointing out that it is unclear whether Kushner has ever visited a Palestinian area (the White House would not say). “There is no indication he is interested in hearing from the other side.’’

Through a White House spokeswoman, Kushner declined to respond or be interviewed.

Last June in Washington, Yousef Al Otaiba, ambassador of the United Arab Emirates, received an unexpected request from his friend Thomas Barrack Jr., a Lebanese-American businessman and Trump fundraiser: Would he meet with Jared Kushner?

“What struck me in our first meeting is that he asked a lot of questions and listened,’’ Otaiba said. Since then, the two have been in close touch, with Kushner asking Otaiba for his impressions of shifting forces in the Middle East, Syria, Iran, extremism, relationships.

Though he had been raised a Democrat, Kushner endorsed Mitt Romney in the 2012 presidential race, in part because of disappointment with President Obama on Israel.

Many foreign policy experts wait their entire careers for a White House job, but Kushner is now fielding inquiries from foreign leaders even as he is learning to navigate the subject.

In his first weeks in the White House, Kushner has had exchanges with officials from Egypt, Saudi Arabia, Mexico and elsewhere, and he has greeted King Abdullah II of Jordan, whom he met several years ago on a trip to that country.

Some observers see Kushner as a welcome counter to an unpredictable president and to firebrands like Stephen Bannon, the White House strategist, and David M. Friedman, the ambassador designate to Israel.

Kushner “could be a moderate voice,’’ said Dan Gillerman, Israel’s former ambassador to the United Nations, who got to know Kushner in New York. “The strange thing is, that 36-year-old kid may end up being the grown-up in the room.’’