A key 2016 campaign antagonist of Donald Trump attended a fundraiser with 2020 Democratic presidential hopeful Joe Biden.

Gold Star parents Khizr and Ghazala Khan clashed with Trump last cycle after their emotional address at the 2016 Democratic National Convention in support of Hillary Clinton's White House bid. Three years later, the couple attended an exclusive event for Biden donors hosted by former Virginia Gov. Terry McAuliffe, another Clinton ally, according to a pool report.

Biden, dipping in and out of his stump speech, described Trump as a man “with very few social[ly] redeeming value[s]" over the weekend. The former vice president, 76, said the Khan family had firsthand experience of “what this man is like” because Trump attacked them after their DNC appearance.

“I know as well, Mr. Khan, what you’ve gone through. I know just what you suffered and the humiliation,” Biden said. “I lost a son too, and I’ve noticed what he’s trying to do to my living son.”

Khizr Khan, a Pakistani immigrant lawyer, lost his son, Humayun Khan, a U.S. Army captain, when a car bomb exploded while he was stationed outside his base in Iraq in 2004. Humayun Khan was posthumously awarded a Bronze Star and Purple Heart.

Khizr Khan drew Trump's ire last election cycle when, after criticizing the then-candidate's rhetoric against Muslims, he pulled out a pocketbook copy of the Constitution at the 2016 Democratic convention in Philadelphia and asked whether Trump had read the document as Ghazala Khan stood by his side.

"I will gladly lend you my copy. In this document, look for the words 'liberty' and 'equal protection of law,'" he said.

In response, Trump questioned whether Ghazala Khan had "not been allowed to have anything to say."

"I was viciously attacked by Mr. Khan at the Democratic Convention. Am I not allowed to respond? Hillary voted for the Iraq war, not me!" he tweeted after hit with a backlash over his comments.

Since Trump's election, Khan advocated against the new administration's so-called Muslim travel ban, among other issues.

Biden's family has also been in Trump's firing line. Trump is the subject of a House Democrat-led impeachment proceeding triggered by accusations that the president leveraged U.S. military aid to pressure Ukraine to dig up political dirt on a domestic political opponent: Joe Biden and his 49-year-old lobbyist son, Hunter Biden.

The younger Biden earned $50,000 a month from 2014 to 2019 as a board member for an oligarch-connected natural gas company in Ukraine while his father spearheaded the Obama administration's policy in the country. Before an October Trump rally, Eric Trump, the incumbent's second son, led a "lock him up" chant directed at both Bidens.