United States President Donald Trump’s younger brother, Robert Trump, has been hospitalised in New York.

The president visited his younger brother Robert in a New York City hospital for about 45 minutes on Friday, before heading for his New Jersey country club where he planned to spend the night.

Trump told a news conference prior to the visit that his brother was in the hospital but did not elaborate on the reason.

“I have a wonderful brother. We’ve had a great relationship for a long time, from day one,” Trump said. “Hopefully he’ll be all right, but he’s having a hard time.”

Robert Trump, one of four siblings to the president, recently filed a lawsuit on behalf of the Trump family seeking to stop publication of a tell-all book by the president’s niece Mary titled ‘Too Much and Never Enough.’

The president has said that Mary Trump’s book was a violation of a nondisclosure agreement she signed in connection to a financial settlement she received from the Trump family.

Mary is the daughter of the brothers’ eldest sibling, Fred Trump Jr., who struggled with alcoholism and died in 1981 at the age of 43.

Robert Trump had previously worked for his older brother as a top executive at the Trump Organisation. Once a regular bold face name in Manhattan’s social pages, he has kept a lower profile in recent years.