Trump’s younger brother, Robert Trump, died on Saturday night aged 71. Trump had met his brother on Friday and said, during a news briefing in the same day, that Robert was "having a hard time" but did not provide details on his condition.
He had also been hospitalized in the intensive care unit for several days in June, reports say.
Following Robert’s death, Biden, the presumptive Democratic presidential candidate, said he understood the "tremendous pain of losing a loved one" in a tweet directed towards Trump.
But the Republican president later shared a video on Twitter that appeared to mock Biden for his stutter and odd things he said in interviews. He did not provide any context for why he shared the video.
This comes as a new opinion poll shows that Biden has a nine percentage-point lead over Trump nationally with less than three months before the 2020 election.
The NBC News-Wall Street Journal poll, released on Sunday, found that 50 percent of registered voters favored Biden while just 41 percent said they would support Trump.