Oscar-winning actor, Joaquin Phoenix, has reportedly welcomed his first child with his fiancé and fellow Hollywood A-lister actress, Rooney Mara. The couple have named their new baby boy after Phoenix's late brother, River, who tragically passed away in 1993 aged just 23 years old.

The joyous news came courtesy of director Victor Kossakovsky, who revealed the new arrival at the 2020 Zurich film festival after a screening of the black-and-white documentary Gunda, on which Joaquin Phoenix is an executive producer.

When asked about Phoenix's involvement in the movie, which looks at the daily life of a pig and its farm animal companions, two cows and a one-legged chicken, Kossakovsky responded saying, "He just got a baby, by the way, his name was... a beautiful son called River, so he cannot promote [the film] right now."

River Phoenix died of an accidental drug overdose in West Hollywood in the early hours of October 31, 1993 aged just 23. Despite his young age, the actor had already proven his talent time and again in such beloved movies as Stand by Me, Indiana Jones and the Last Crusade, and My Own Private Idaho alongside Keanu Reeves. Joaquin Phoenix recently discussed both the personal loss of his brother and the loss to cinema when talking with Anderson Cooper on 60 Minutes. "River was a really substantial actor and movie star, and we didn't really know it," he said. "So during that time in which you're most vulnerable, there are helicopters flying over. There are people that are trying to sneak on to your land. Certainly, for me, it felt like it impeded on the mourning process."

Joaquin Phoenix and Rooney Mara first met back in 2013 while working on Spike Jonze's sci-fi romance, Her. They have appeared together on screen several times since, in the movies Don't Worry, He Won't Get Far on Foot and the drama Mary Magdalene, which is when they began dating. The couple confirmed their engagement in May last year.

Mara, who is best known for roles in the likes of The Social Network and The Girl with the Dragon Tattoo, has several projects due for release, including the biographical thriller A House in the Sky and director Guillermo del Toro's Nightmare Alley. Phoenix meanwhile recently took home the Academy Award for best actor for his portrayal of the iconic Batman villain, Joker. While the movie was thought to be standalone, there have been murmurs of several Joker sequels being considered, with Phoenix reportedly offered $50 million to return. That's a whole lot of baby formula.

One insider reportedly said that, "Joaquin initially felt Joker was a standalone movie. But he's changed his tune now. He says he wants to play this character again, despite the controversies that came with the release last year. It's still being negotiated but the scripts are being written and Joaquin is very engaged with it." Considering both the critical and financial success of the first Joker, it would not be too surprising if both the actor and studio wanted to build on it.

The news of the birth of Phoenix and Mara's son, River, was revealed at the 2020 Zurich Film Festival.