Joaquin Phoenix and Rooney Mara welcome baby boy, named after Phoenix's late brother, River, director says

Actors Joaquin Phoenix and Rooney Mara have welcomed their first child, a baby boy they have given a meaningful name, according to director Viktor Kossakovsky.

During a question and answer session at the Zurich Film Festival, Kossakovsky was asked about Phoenix's involvement in the documentary "Gunda." Kossakovsky, who directed the film about animal rights, explained how he got Phoenix to sign on as executive producer — then he revealed much more.

Kossakovsky said Phoenix just welcomed a baby. "A beautiful son called River," the director added.

Phoenix's brother, actor River Phoenix, died of a drug overdose in 1993. He was just 23.

Joaquin Phoenix, and sister Rain Phoenix, were with River when he died. The family has rarely spoken about River's death publicly — until Joaquin and several members of the acting family granted a rare interview to Anderson Cooper for CBS News' "60 Minutes" earlier this year.

"I mean, River was a really substantial actor and movie star, and we didn't really know it," Joaquin said about his brother. "And so during that time in which you're most vulnerable, there are helicopters flying over. There are people that are trying to sneak onto your land. Certainly, for me, it felt like it impeded on the mourning process, right?"

His mother, Heart, said "the grieving process happens out of nowhere."

"I'll be driving and all of a sudden, I will feel it. And I'll just welcome it," she told Cooper. 

Heart and Joaquin's stepfather, Jeffrey, run a non-profit in River's name called The River Phoenix Center for Peacebuilding, which works on social justice issues and conflict resolution. Rain Phoenix, a musician, has released an album dedicated to her brother called "River."

"I feel like in virtually every movie that I made, there was a connection to River in some way," Joaquin told Cooper during the interview. "And I think that we've all felt his presence and guidance in our lives in numerous ways."

Now, Phoenix and Mara — who met while filming "Her" in 2013 and worked together again filming "Mary Magdalene" in 2016 — are strengthening that connection to River with their newborn son, according to Kossakovsky. However, the notoriously private couple has not publicly announced the birth of their son.