Katherine "Kitty" Oppenheimer, née Puening, married the scientist in 1940, only two years before he joined the Manhattan Project.

Kitty had been married three times before, as she wed musician Frank Ramseyer in 1932 before their marriage was annulled in 1933. 

Shortly afterward, in 1934, she was involved with the Communist Party of America, and became John Dullet Jr.'s. common-law wife when they lived together in Chicago, before separating in 1936.

Kitty then married Oxford doctor Richard Stewart Harrison in 1938, but had an affair with Oppenheimer while Harrison was working in California. She divorced Harrison in 1940, and married Oppenheimer a day later. 

They remained married until Oppenheimer's death from throat cancer in 1967, and Kitty scattered his ashes into the water by the island of St. John in the Virgin Islands, where they had spent plenty of time with their children, Peter and Toni.

Kitty spent the rest of her life with Robert Serber, another physicist from the Manhattan Project, whose wife had died by suicide. Kitty died in hospital in 1972, just as the pair had set out to go sailing to Japan, the Galapagos Islands, and Tahiti.

Oppenheimer had two children with his wife, Kitty. Their oldest child, Peter, was born in Pasadena, California, in May 1941, before the family moved to Los Alamos for the Manhattan Project.

When Peter was just two months old, the Oppenheimers left him with friends Haakon and Barbara Chevalier, according to "American Prometheus." Robert said his wife was exhausted. The couple then spent two months at the family's ranch, Perro Caliente, in New Mexico.

According to the Nuclear Museum, Peter struggled with anxiety as a child and didn't have a good relationship with his mother. 

"Robert thought that, in their highly charged, passionate, falling in love, that Peter had come too soon, and that Kitty resented him for that reason," Oppenheimer's secretary, Verna Hobson, said during a 1979 interview.

When his father died in 1967, Peter moved back to the family's Perro Caliente ranch in New Mexico. He's worked as a carpenter over the years and has three children.

Toni Oppenheimer was born in 1944 and lived at Los Alamos until she was three. That's when her father became director of the Institute for Advanced Study and moved the family to Princeton, New Jersey.

As a baby, Toni lived with the Oppenheimers' friend Pat Sherr for several months. Robert visited regularly but asked if she wanted to adopt Toni, Sherr later recalled. When Sherr asked him why, he said, "Because I can't love her," adding that he wasn't "an attached kind of person." 

However, a childhood friend of Toni's described Robert as a "loving dad" in an April interview with The Winchester Star.

Toni had polio when she was young, which is largely why the family started visiting St. John in the Virgin Islands; the warmth seemed to help her condition.

Toni had a complicated relationship with her mother, largely because of Kitty's alcohol use. 

"She leaned on Toni an awful lot and it was difficult for her in that way, but she wanted only good and happiness for Toni," Hobson said of Kitty in 1979. 

Two years after Robert's death in 1967, the United Nations rejected Toni's application to become a translator. The FBI wouldn't grant her the appropriate security clearance for the job.

She struggled to cope with losing her father and her job opportunity, and after living on the island of St. John for a while, she died by suicide in January 1977, just a month after she turned 32.

Although Toni didn't have any children before her death, Peter Oppenheimer has three: Charles, Ella, and Dorothy. 

Dorothy Vanderford, who was born in 1973, is Oppenheimer's oldest grandchild. She works in the nuclear industry and has a PhD in English. 

In 2023, she spoke to KSNV about the film and said that Christopher Nolan didn't consult the family about making his movie.

After seeing the movie, she said, "There were a few things that I didn't agree with and didn't like, but overall I felt like it was a good movie."

Charles Oppenheimer was born in 1975 and has worked in software development for many years. 

The youngest sibling, Ella, keeps her life private. 

Both Dorothy and Charles took part in a lengthy interview in 2015 about their grandfather for the Atomic Heritage Foundation.

At the time, Charles said that many historians find his grandfather a mysterious figure.

"In particular, people are having a hard time pinning down who this guy was. I guess it's made it difficult to deal with for the family, for some people. Not for me," he said.

Charles has two daughters with his wife, Karen Pak Oppenheimer, which means that Oppenheimer has at least two great-grandchildren.

Both Charles and his wife are co-executive directors of the Oppenheimer Project, which honors Robert's legacy. 

In a recent essay for The New York Times, Charles wrote that nuclear war would end the world as we know it. "I'm not afraid to be the voice calling for increased unity in the world, even though my grandfather was eventually attacked for this," he wrote.  

This story was originally published in July 2023 and was updated on December 17, 2024.