In an interview, Eric Danziger, the head of Trump Hotels, disputed that teaming up with the Kushners might pose a conflict.

“This is a straight-up business deal,” he said. “If there were something out of the ordinary about the deal, then I think that question is fair,” he said, but “we do market transactions that are reviewed and checked.”

Mr. Danziger said that Bobby Burchfield, the Trump Organization’s outside ethics adviser, had asked about the financing involved in a potential Long Branch deal with the Kushners. Mr. Burchfield, who scrutinizes how the Trump Organization’s partners finance deals, among other things, often requires more information before approving a deal.

Whether or not the Trumps and Kushners reach a deal, Mr. Kushner stands to gain. He is expected to eventually own 20 percent of the hotel in Pier Village, according to documents obtained through a public records request. And he was personally involved in the project early in the presidential campaign. In documents provided to Long Branch, the Kushner Companies stated that Mr. Kushner “is strictly a passive investor.”

He also retains a stake in a Kushner residential tower in Jersey City that bears the Trump name.

In Livingston, Mr. Kushner has divested from the Westminster Hotel, a three-story property overlooking strip malls. While it is unusual for the Trumps to manage hotels that do not carry one of their brands, Mr. Danziger said he was discussing similar deals with other companies as a way to expand the business under the “right circumstances.”

“An owner wants to know they can depend on and rely on the operator, and we have a lot of credibility as operators,” he said.

The growing relationship between the families could be helpful to the Trumps, as the ethical restraints they voluntarily adopted after the election have proved to be a hindrance to new business. The Trump Organization, which agreed not to start any new foreign projects during the presidency, has yet to open a new hotel in the United States since Mr. Trump took office.