(CNN) Joaquin Phoenix is known for being extremely private and rarely mentions his late brother, River.

But the actor is in the spotlight at the moment with all the buzz surrounding his forthcoming Batman spin-off film, "Joker," and has used the attention to pay homage to his legendary sibling.

Phoenix thanked his late brother during an emotional acceptance speech Monday at the Toronto International Film Festival after he was awarded the TIFF Tribute Actor Award.

"When I was 15 or 16, my brother River came home from work and he had a VHS copy of a movie called 'Raging Bull,' and he sat me down and made me watch it," Phoenix said. "And the next day he woke me up, and he made me watch it again. And he said, 'You're going to start acting again, this is what you're going to do.'"

Joaquin Phoenix attends the "Joker" premiere Monday during the 2019 Toronto International Film Festival.

The actor went on to say, "He didn't ask me, he told me. And I am indebted to him for that because acting has given me such an incredible life."

Read More