The Kushners have weathered ordeals before and emerged stronger and more prosperous. In 2004, Charles Kushner pleaded guilty to 18 counts of witness retaliation, tax violations and false statements to the Federal Election Commission after he hired a prostitute in a scheme to entrap and retaliate against his brother-in-law, who he suspected was cooperating with a federal inquiry into his business.

Charles Kushner still does not speak to his brother, whom he publicly blamed for instigating the investigation that led to his two-year prison sentence. Asked whether he hoped for presidential absolution, Mr. Kushner said, “I would prefer not to have a pardon” because it would trigger only further publicity.

His real estate empire is now under a national microscope, its every deal scrutinized for hints of federal influence. And while Charles Kushner insists his bankers are loyal, investors are eager and deals are plentiful, some business associates say the drumbeat of unflattering headlines is putting tremendous pressure on the family business. Banks must assess the risk of any continuing regulatory or criminal inquiries before making loans; potential investors are worried that they could come under scrutiny or that projects will be delayed or fall apart.

Mr. Kushner scoffs at such fears. “We are actively involved in more than $3 billion of projects and banks are providing $1.5 billion of financing in the first six months of this year,” he said. “Does that seem like we are lacking in funds?”

That said, the company has been forced to rule out two major sources of financing — foreign nations’ sovereign wealth funds and a federal program that offers foreign investors a path to citizenship — after questions about the propriety of tapping them given Jared Kushner’s foreign policy influence. While Mr. Kushner transferred some holdings in Kushner Companies to a trust run by his mother, he retains the vast majority — holdings estimated to be worth at least $761 million.

Avoiding such entanglements has proved harder, company officials said, than they expected. Bloomberg recently reported that two months after Mr. Kushner joined the White House, the firm sold a stake in a Brooklyn building to an entity whose largest shareholder is the Japanese government. A spokesman said Kushner company officials were unaware of the Japanese government’s involvement until the news report.

The finance minister of the tiny, oil-rich Gulf nation of Qatar also met separately early last year with both Josh and Charles Kushner at a time when the Qataris were seeking White House support against their powerful regional rivals. Josh Kushner, who runs the investment firm Thrive Capital, which recently raised a $700 million fund, cleared the meeting with outside counsel beforehand, his spokesman said.