15 members of Kennedy family endorse Biden in rebuke to RFK Jr.

FILE-President Joe Biden delivers the annual State of the Union address before a joint session of Congress in the House chamber at the Capital building on March 7, 2024 in Washington, D.C. (Photo by Shawn Thew-Pool/Getty Images)

The Kennedy family will endorse President Joe Biden during his reelection campaign event in Philadelphia on Thursday, a condemnation of the candidacy of Robert F. Kennedy Jr. 

Democrats and Republicans worry that Kennedy’s candidacy could spoil Biden and Donald Trump’s presumptive campaigns.

How many Kennedy family members are endorsing Biden?

The president will accept endorsements from at least 15 members. Kerry Kennedy, a daughter of former Attorney General Robert F. Kennedy, niece of former President John F. Kennedy, and sister of the current presidential contender, will deliver the endorsement of Biden, the Biden campaign announced.

RELATED: Who is Nicole Shanahan, RFK Jr.’s running mate?

According to the Associated Press, some Kennedy family members were not endorsing Biden, including U.S. Ambassador to Australia Caroline Kennedy and nonprofit leader Maria Shriver, which the Biden campaign said was due to their nonpolitical professional roles.

Why isn’t RFK Jr.’s family endorsing him?

Robert Kennedy Jr. has spoken publicly in the past about disagreeing with his family on many issues.

After a Super PAC supporting his campaign produced a Super Bowl ad that relied on imagery from John F. Kennedy’s 1960 presidential run. 

RELATED: Robert Kennedy ad plays during the Super Bowl, uses JFK jingle

Kennedy Jr. apologized to his relatives on the X social media platform, saying he was sorry if the spot "caused anyone in my family pain."

What does Kennedy family endorsement mean for Biden?

The decision to highlight the Kennedy family endorsement over six months from Election Day is an indication of how seriously the Biden administration is taking the threat of Robert F. Kennedy Jr.’s long-shot odds to be president as he may attempt to siphon off support from the president.

Who is RFK Jr.?

Kennedy, 70, is a member of perhaps the nation’s most famous political dynasty. His uncle was President John F. Kennedy and his father served as attorney general and a U.S. senator before seeking the Democratic nomination for president. Both were assassinated.

RELATED: Robert F. Kennedy Jr. to run for president as independent and drop his Democratic primary bid

RFK Jr. built a reputation of his own as an activist, author, and lawyer who fought for environmental causes such as clean water. The AP noted that his activism has veered into conspiracies and contradicted scientific consensus, most infamously on vaccines. 

After the formal endorsement, Biden and members of the Kennedy family were set to meet with supporters at a campaign event, and members of the Kennedy group planned to make calls to voters and knock on doors on Biden's behalf, the AP reported. 

The Associated Press contributed to this report. This story was reported from Washington, D.C.