Rain Phoenix posts birthday tribute to brother River

River Phoenix's sister Rain Phoenix has paid a touching tribute to the late actor on what would have been his 54th birthday.

In an Instagram post, the singer and actor shared a series of images of and quotes by the Stand By Me star. She captioned the post "Happy Birthday River."

The carousel of photos were accompanied by her brother's own words relating to a raft of humanitarian causes, including environmentalism, LGBTQ+ equality and plant-based eating.

"If I have some celebrity, I hope I can use it to make a difference," one quote reads. "The true social reward is that I can speak my mind and share my thoughts about the environment and civilisation itself."

Another excerpt reads, "We're all worth it man. We're all worth millions of planets and stars and galaxies and universes."

Phoenix died on 31 October 1993 from a drug overdose. He was 23.

Red Hot Chili Peppers bassist Flea, who accompanied Phoenix to the hospital after the actor collapsed at The Viper Room, commented, "Happy birthday most beautiful one."

Dermot Mulroney, who starred alongside the young actor in 1993's The Thing Called Love, commented, "Happy Birthday River - my inspiration."

Phoenix was nominated for a Best Supporting Actor Oscar for his role in Running on Empty. His best-known films include Stand By Me opposite Kiefer Sutherland, The Mosquito Coast with Harrison Ford and Helen Mirren, and My Own Private Idaho with Keanu Reeves.