Oscar-winning Joker actor Joaquin Phoenix is said to have welcomed his first child, a son, with fiancee Rooney Mara and has named him after his late brother River.

The news came to light at the 2020 Zurich Film Festival where director Victor Kossakovsky, who worked with Phoenix on film Gunda, answered a question about how he got the star involved in the movie.

He said: “He just got a baby by the way... A beautiful son called River.”

Phoenix and Mara have not confirmed the birth of a son and they didn’t announce that Mara was pregnant. The couple have been dating since 2016.

Phoenix recently spoke about his brother, who died from a drug overdose in 1993, in an interview with 60 Minutes.

He said: "We were so removed from kind of the entertainment world. We didn't watch entertainment shows. We didn't have the entertainment magazines in our house. 

“I mean, River was a really substantial actor and movie star, and we didn't really know it. 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?”