The specific details surrounding the younger Trump’s condition remain unknown.
But the 72-year-old was reported to have spent at least 10 days in the neurosciences intensive care unit of a Manhattan hospital in June.
Although quite private, Robert has been in the news recently after he led a lawsuit on behalf of the Trump family seeking to stop publication of a tell-all book by the President’s niece, Mary, entitled Too Much And Never Enough.
The Trump family claimed her book was a violation of a nondisclosure agreement she signed dating back to an inheritance dispute in the family.
Robert, the youngest Trump sibling, said at the time he was “deeply disappointed” in his niece’s decision to write such a book.
He added the entire family were “so proud of my wonderful brother, the President”.
In tweets last month, the President attacked his niece.
He said: “Mary Trump, a seldom-seen niece who knows little about me, says untruthful things about my wonderful parents [who couldn’t stand her] and me, and violated her nondisclosure agreement.
“She also broke the law by giving out my tax returns. She’s a mess.
“Many books have been written about me, some good, some bad.
“Both happily and sadly, there will be more to come.”