"Grace and I have a child with autism and we believe it is critical that all of the issues surrounding the causes of autism be openly discussed and examined," De Niro, 72, had said in a statement amid controversy swirling around the planned screening of the anti-vaccination documentary Vaxxed at the Tribeca Film Festival. (He later decided to pull the film from the festival's schedule.)
While this is the first time the actor has confirmed his child's diagnosis, it's not the first time De Niro has associated himself with a film on the topic of autism. At the 2014 festival, he and his wife hosted a screening of the documentary Sounding the Alarm.
While De Niro has mostly kept his private life out of the spotlight, in the past he's hinted at the experience of raising a child with special needs.
In a 2013 interview with Katie Couric, De Niro broke down while discussing the film Silver Linings Playbook, saying he can relate to director David O. Russell, who wrote the film for his son who has bipolar disorder.
"I don't like to get emotional," he said. "But I know exactly what he goes through."
De Niro, who has two children with Hightower – son Elliot, 18, and daughter Helen Grace, 4 – also has four other children: daughter Drena, 40, and son Raphael, 35, with former wife Diahnne Abbott, as well as 16-year-old twin sons Julian and Aaron, born via surrogate with ex-girlfriend Toukie Smith.
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And while De Niro is known to be a man of few words, the actor has often shown his softer side while speaking about his family.
"There are great moments and moments of sadness," he previously told PEOPLE of raising his kids. "Sometimes you're the last person they want to deal with. It's like when you walk your kids to school and they get older and they don't want to hold your hand or kiss you goodbye."
Still, De Niro says he's grateful to have his children nearby.
"Everybody's in New York and, hopefully, my younger kids will go to college in New York and find something they want to do so they'll stay in the city," De Niro told the Los Angeles Times. "I like the kids to be around. If they want to go to college here and live at home, I won't have a problem with that."