Robert Trump, the younger brother of the US president, has died aged 72, the White House has confirmed.
Robert Trump, pictured here after his brother's election win in 2016, used to manage Trump's real-estate investments. Photo: AFP / 2016 Getty Images
"He was not just my brother, he was my best friend," Donald Trump said in a statement today.
The president had visited his brother in hospital in New York on Friday afternoon, telling reporters: "He's having a hard time."
US media reports had said Robert Trump was seriously ill, but it is unclear what he was suffering from.
"It is with heavy heart I share that my wonderful brother, Robert, peacefully passed away tonight," the president said. "His memory will live on in my heart forever."
Robert Trump was the youngest of the five Trump siblings, born two years after Donald.
He spent much of his career with the family real-estate firm, becoming a top executive. Unlike his brother, however, he was said not to court publicity and lived semi-retired in New York state.
He recently went to court in a failed bid to stop publication of his niece Mary Trump's tell-all book about the president, How My Family Created the World's Most Dangerous Man.
According to the New York Post, Robert spent more than a week in the intensive-care unit of Manhattan's Mount Sinai Hospital in June.
The newspaper reported in March that Robert Trump had married his second wife, Ann Marie Pallan, and that they lived in a country home on Long Island.
Two of Donald Trump's children expressed sadness about their uncle's death.
"Robert Trump was an incredible man - strong, kind and loyal to the core. Anyone who encountered him felt his warmth immediately. He will be deeply missed by our entire family," said Eric Trump in a tweet.
"Uncle Robert, we love you. You are in our hearts and prayers, always," tweeted Ivanka Trump.
- BBC / Reuters