Jared Kushner, the president’s son-in-law and senior adviser, didn’t identify on his government financial disclosure form that he is currently a part-owner of a real-estate finance startup and has a number of loans from banks on properties he co-owns, according to securities filings. Mr. Kushner’s stake in Cadre—a tech startup that pairs investors with big real-estate projects—means the senior White House official is currently a business partner of Goldman Sachs Group Inc.GS 0.47%▲ and billionaires including George Soros and Peter Thiel, according to people close to the company. The Cadre stake is one of many interests—and ties to large financial institutions—that Mr. Kushner didn’t identify on his disclosure form, according to a Wall Street Journal review of securities and other filings. Others…