Robert Trump, the younger brother of US President Donald Trump and a business executive who avoided the spotlight, died on Saturday.
Trump announced the death in a statement.
"It is with a heavy heart I share that my wonderful brother, Robert, peacefully passed away tonight. He was not just my brother, he was my best friend," Trump said.
"He will be greatly missed, but we will meet again. His memory will live on in my heart forever. Robert, I love you. Rest in peace."
Robert Trump, 71, was a business executive and real estate developer. Unlike his reality TV star brother, Robert shunned the limelight.
Trump had visited his brother on Friday at the New York hospital before going to his golf club at Bedminster for the weekend.
The president was expected to attend the funeral, an aide said. He has a busy travel schedule in the coming days with plans to visit four battleground states as part of his re-election campaign.
The cause of death was not revealed.
Trump told reporters on Friday that his brother was "having a hard time" with an undisclosed illness.
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.