Jared Kushner, the president’s son-in-law and senior adviser, is currently in business with Goldman Sachs Group Inc. and billionaires George Soros and Peter Thiel, according to people familiar with the matter and securities filings.

The previously undisclosed business relationships with titans of the financial and technology worlds are through a real-estate tech startup called Cadre that Mr. Kushner cofounded and currently partly owns.

Goldman and Messrs. Soros and Thiel, as well as other billionaires’ firms, also have stakes in the company, which is based in a Manhattan building owned by the Kushner family’s company, according to people close to Cadre.

The Cadre stake is one of many interests—and ties to large financial institutions—that Mr. Kushner didn’t identify on his government financial-disclosure form, according to a Wall Street Journal review of securities and other filings. Others include loans totaling at least $1 billion, from more than 20 lenders, to properties and companies part-owned by Mr. Kushner, the Journal found. He has also provided personal guarantees on more than $300 million of the debt, according to the analysis.

In his disclosure form filed earlier this year, Mr. Kushner didn’t identify Cadre as among his hundreds of assets. The Journal identified his Cadre stake through a review of securities and other filings as well as interviews with people familiar with the company and Mr. Kushner’s finances.