4:02 PM PT -- Jane Fonda has reacted to her little brother's passing, saying, "I am very sad. He was my sweet-hearted baby brother. The talker of the family. I have had beautiful alone time with him these last days. He went out laughing."
Hollywood icon Peter Fonda is easy riding into the sunset -- the veteran actor died Friday ... TMZ has learned.
A rep for Peter confirms he passed Friday morning at his his home in Los Angeles, and was surrounded by family. We're told the official cause of death was respiratory failure due to lung cancer -- and he had been in and out of the hospital recently.
Peter, is Jane Fonda's brother and the son of Henry Fonda. The family released a statement, saying, "In one of the saddest moments of our lives, we are not able to find the appropriate words to express the pain in our hearts."
They added, "While we mourn the loss of this sweet and gracious man, we also wish for all to celebrate his indomitable spirit and and love of life."
Peter's most famous for his iconic role in the 1969 counterculture classic, "Easy Rider" ... which he co-wrote and produced. He also costarred with Dennis Hopper and Jack Nicholson.
The 50th anniversary of the film just past on July 14th, and Peter was planning a concert and screening for September to celebrate.