River Phoenix's Mom, Sister Pay Tribute to Late Actor on His Birthday: 'He Remains a Guiding Light'

George Rose/Getty River Phoenix in 1988

River Phoenix's family members are remembering him on what would've been his 52nd birthday.

On Tuesday, the late actor's mother Arlyn "Heart" Phoenix shared a throwback black-and-white photo of herself and River alongside a heartfelt caption that began, "On August 23, 1970, at 12:03 PM in a little town called Madras in Oregon, I became a mother."

She continued, "52 years ago I experienced a LOVE beyond all of my understanding which transformed my life and multiplied in and out of my being. During the past years since I have posted on Facebook, I have shared how deeply his life and passing affected me. He remains a guiding light on my pathway forward."

Heart concluded, "When I am reminded of the lyrics to a song River wrote at 15, 'RUN TO THE RESCUE WITH LOVE AND PEACE WILL FOLLOW,' I am ever grateful for this inspiration which is foundational to the work of The River Phoenix Center for Peacebuilding!"

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RELATED: All About River Phoenix, the Late Actor Brother Joaquin and Rooney Mara Named Their Child After

The actor's younger sister Rain Phoenix posted her own tribute to River, sharing a photo of the actor holding up one hand, concealing half his face.

"Happy birthday River 💙," she wrote, going on to quote lyrics from her song "Immolate": "I'm only as good as your friendship has made me ... "

"On the death of a friend, we should consider that the fates through confidence have devolved on us the task of a double living, that we have henceforth to fulfill the promise of our friend's life also, in our own, to the world," added Rain, 49, attributing the latter passage to Henry David Thoreau.

River was just 23 when he died outside the Viper Room in West Hollywood, California, due to a drug overdose on Oct. 31, 1993. He made his mark on the world after starring in the beloved films Stand By Me (1986), Running on Empty (1988) and My Own Private Idaho (1991). His final film, Dark Blood, was completed in 2012.

RELATED VIDEO: Joaquin Phoenix Recites Late Brother River's Song Lyrics in Emotional Oscars Speech for Joker

During the 2020 Academy Awards, younger brother Joaquin Phoenix paid tribute to River while accepting the Best Actor Oscar for Joker, reciting a lyric written by his late brother.

"I've been a scoundrel all my life. I've been selfish. I've been cruel at times, hard to work with, and I'm grateful that so many of you in this room have given me a second chance," he told the audience. "And I think that's when we're at our best, when we support each other. Not when we cancel each other out for past mistakes, but when we help each other grow, when we educate each other, when we guide each other towards redemption. That is the best of humanity."

"When he was when he was 17, my brother wrote this lyric," Joaquin, 47, went on. "He said, 'Run to the rescue with love and peace will follow.' "

Later that year, Joaquin welcomed his first child with Rooney Mara: son River, named after Joaquin's late brother.