Nicole Kushner Meyer used her brother's name while promoting an investment-for-visas scheme in Beijing and Shanghai.
Critics were quick to accuse the family business of playing up its connection to the White House at the event.
But the company said on Monday the comments were misconstrued and Ms Meyer was only pointing out he left the firm.
"Ms Meyer wanted to make clear that her brother had stepped away from the company in January and has nothing to do with this project," said Risa Heller, a Kushner Companies spokeswoman.
"Kushner Companies apologises if that mention of her brother was in any way interpreted as an attempt to lure investors. That was not Ms Meyer's intention."
Mr Kushner, 36, who is married to President Trump's daughter, Ivanka, and serves as a White House senior adviser, has come under scrutiny for his private business interests.
Government ethics laws bar government officials from profiting personally from their roles.
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Ms Meyer mentioned her brother on Saturday and Sunday while urging investors to put $500,000 (Â£386,500) into a New Jersey real estate project in exchange for investor visas and residency cards in the US through the so-called EB-5 programme.
The EB-5 visa programme, often used by wealthy Chinese nationals, allows foreign investors a path to a green card if they invest more than $500,000 in a project that creates jobs in the US.
Critics of the programme say it used as a means of cheap financing for real estate developers.
Ms Meyer brought up her brother as the company's former chief executive before he left in January to join the Trump administration.
She then said the Jersey City project, which the company is developing with real estate firm KABR group, "means a lot to me and my entire family", the New York Times reported.
About 15% of the $976.4m-project, known as One Journal Square, will be funded through the EB-5 programme, according to Kushner Companies.
The company also featured a photo of President Trump  on a slide at the event that said "key decision makers" on the EB-5 programme, CNN reported.
The White House said on Monday that it was "evaluating wholesale reform" on the programme to make sure it it was "used as intended and that investment is being spread to all areas of the country".
The administration also said it was "exploring the possibility of raising the price of the visa to further bring the programme in line with its intent".
Reforming visa programmes has been a key part of Mr Trump's immigration policy.
Mr Kushner has said he stepped away from his family's business operations, but government ethics filings show that he and his wife, Ivanka Trump, continue to benefit from their stake in Kushner Companies.
The president's son-in-law, who has no prior government experience, has been entrusted to broker Israeli-Palestinian peace talks and also serves as the lead adviser on relations with China, Mexico and Canada.
Blake Roberts, Mr Kushner's attorney, said on Saturday that he has divested his interests in the One Journal Square project.
"As previously stated, he will recuse from particular matters concerning the EB-5 visa program," Mr Roberts said in a statement.
A company owned by the family of Jared Kushner, Donald Trump's son-in-law and senior adviser, has apologised for mentioning him at a Chinese conference.