Robert F. Kennedy Jr. is an “outlier in the Kennedy family” with his anti-vaxx support, according to his siblings and his niece.

Former Maryland Lt. Gov. Kathleen Kennedy Townsend (his sister), former U.S. Rep. Joseph P. Kennedy II (his brother) and Maeve Kennedy McKean (his niece) call out the son of late presidential candidate Robert F. Kennedy in a Politico op-ed published Wednesday entitled, “RFK Jr. Is Our Brother and Uncle. He’s Tragically Wrong About Vaccines.”

The related co-authors refer to RFK Jr.’s “work against vaccines,” which includes being chairman of the board of Children’s Health Defense. The organization has linked inoculations to autism and food allergies (which has been discredited by scientific studies), and has also claimed that media coverage of the measles outbreak is being “orchestrated” by the World Health Organization.

“ “Robert F. Kennedy Jr. — Joe and Kathleen’s brother and Maeve’s uncle — is part of this campaign to attack the institutions committed to reducing the tragedy of preventable infectious diseases. He has helped to spread dangerous misinformation over social media and is complicit in sowing distrust of the science behind vaccines.” ”

The opinion piece highlights the current measles outbreaks (around 700 cases in the U.S. this year, and a 300% increase in measles being reported world-wide) as well as how immunizations prevent between 2 million to 3 million deaths annually, and have the potential to save 1.5 million more lives each year with broader coverage. The writers also note their family legacy of backing immunization campaigns across the country, such as when President John F. Kennedy urged 80 million Americans to get the Salk polio vaccine in 1961, as well as his signing the Vaccination Assistance Act in 1962 to protect the population, and preschool children in particular.

“ “And we are proud of the history of our family as advocates of public health and promoters of immunization campaigns to bring lifesaving vaccines to the poorest and most remote corners of America and the world, where children are the least likely to receive their full course of vaccinations. On this issue, Bobby is an outlier in the Kennedy family.” ”

“We love Bobby. He is one of the great champions of the environment,” they added. “However, on vaccines he is wrong.”

RFK Jr. responded in a statement to the New York Times that, “I am not anti vaccine. I want safe vaccines with robust safety testing.”

The growing measles crisis has spurred many public figures to make peace with their previous immunization stances. Maureen McCormick, who played Marcia Brady on “The Brandy Brunch,” revealed last month that she regrets a 1969 episode where her character appeared to support getting measles. The scene has been appropriated in anti-vaxx memes and videos.

And President Trump recently pushed for Americans to get vaccinated, telling the press that people “have to get the shots,” in contrast to a series of tweets he sent in 2014 that appeared to link vaccinations with autism.