When Jared Kushner assumed the role of First Son-in-Law, he did so with a massive family debt hanging over his head: 666 Fifth Avenue, the little-loved, 41-story office tower that Kushner Cos. bought on the eve of the financial crisis for a then-unprecedented $1.8 billion. The deal, unsurprisingly, has been something of a disaster. The Kushners, who put up $50 million and borrowed the rest, now own around half the place with their partner, Vornado, along with a crushing $1.2 billion mortgage that comes due in February 2019. The Kushners approached the problem with Trumpian flair, floating an ambitious, now defunct plan to secure $7.5 billion in a Zaha Hadid-led redesign. (Hadid, like the investment’s prospects, has since died.) But while the family has suggested that 666 is but a tiny piece of a huge portfolio that can sustain any kind of setback, it turns out that said portfolio is much smaller than Jared & Co. would have the public believe.

To hear Kushner Cos. tell it, they’re major players in the New York real-estate market, with $7 billion in acquisitions since 2007 and a portfolio that includes “20,000 multifamily apartments [and] 13 million square feet of office, hotel, industrial, and retail space.” But according to an investigation by Bloomberg, those numbers include funds invested by Kushner Cos. partners and properties in which their ownership, in some cases, is less than 5 percent. Owning buildings, of course, is not the only way to command power and money in the real-estate industry; by acting as general partners, the First Family-in-Law has made a nice chunk of change through management fees and clauses that “allow operators to capture outsize gains if they exceed investment targets.” But on their Web site and in their promotional materials, the Kushners haven’t bothered to correct the impression that they own half of Manhattan and large swaths of Brooklyn.

That might have been well and good for the Kushners, if slightly embarrassing, were it not for the fact that a year ago, young Jared became a senior adviser to the president of the United States. Which makes the fact that Kushner Cos. is the minority owner on many of their investments a bit more complicated.

As his family has hunted for investors overseas in countries as far-flung as China and Saudi Arabia, many inside and outside of government worry about the potential for quid-pro-quos—public policy driven by private business. In the partnerships where the Kushner Cos. have minor stakes, there’s pressure to make returns for the investors who put up most of the money.

Kushner Cos. says there is no interplay between politics and its business. Jared Kushner has divested from some assets and says he has no involvement in the business any more, although ethics experts say his divestment to close family members is still cause for concern.

Others don’t see it as so cut and dried. “Jared Kushner had a very significant role in the company,” former International Monetary Fund ethics adviser Virginia Canter told Bloomberg. “He apparently did many of these deals and built relationships with these investors. That may give him a sense of responsibility that you really can’t just sever. And we don’t know what their priorities are. The investors may have their own agenda which could act as influences on him in an official capacity.” (Kushner Cos. has said that Jared Kushner’s politics and position are unrelated to its business.)

Unfortunately, none of the would-be investors they’ve approached about their plan to turn 666 around have been game. (The Chinese insurance giant Anbang, for one, famously backed out of a potential deal after experts raised alarms that the terms were unusually favorable.) And Vornado C.E.O. Steve Roth, whose company co-owns 666, has said the harebrained redesign scheme is not happening. That means the Kushners will likely have to renegotiate with lenders and, according to people familiar with the company, potentially lose “some, or even all, of their share in the building.”