The Celebrity Rehab alum had been in a medically induced coma in critical condition after he was found unconscious earlier this month.
"Jeff was taken off life-support [Thursday] afternoon," his manager, Phil Brock, tells PEOPLE. "His family chose to take him off of life-support based on advice from physicians. They thought for several days that the situation was hopeless."
Conaway died at 10:30 a.m. at a Los Angeles-area hospital. He was surrounded by his sisters, nieces and nephews, Brock says.
'Kind, Gentle Soul'"We loved Jeff as a person. We respect him. We know his personal struggles are all over," says Brock. "He was a kind, gentle soul who loved to perform, from small theater to Broadway."
Dr. Drew Pinsky, who had seen Conaway during the recent hospitalization, said the actor had suffered pneumonia and the effects of too much prescription medication.
"There is no evidence showing Jeff died from an overdose," he said. "Jeff is another example of a pharmaceutical death from the overutilization of prescription drugs. Please continue to pray for friends and family. They appreciate your support.”
Conaway got his start when his mother, a struggling actress named Mary Ann Brooks, brought him along to her audition for Broadway's All the Way Home. He ended up getting a part, but his mom wasn't cast. More stage roles followed, then modeling jobs and TV commercials for Clairol, Fab detergent and other products.
At 15, Conaway tried out for the singer's slot in a rock band and within a week was on the road. It was then, he later said, that he got his first taste of drugs. Although he insisted his own habits were limited to coke, pills and pot, within two years "all my friends were junkies," he said. "I figured if I ended up as a musician, I'd have died."
The Road to GreaseInstead, he enrolled in the North Carolina School of the Arts for a year, then switched to New York University, where he took dance classes from Martha Graham and acting classes from Olympia Dukakis.
But by the mid-'80s, his personal and professional lives were spiraling downwards.
He broke his four-year contract with Taxi in 1981, and his five-year marriage to Rona Newton-John (sister of Grease star Olivia Newton-John), whom he had met at a cast party, hit the rocks. She was seven years his senior and had a son from a previous marriage.
"We were always fighting," Conaway told PEOPLE. "She had a problem with identity, being that her sister was such a big star and I was getting a lot of attention at that time."
The couple, who had no children together, divorced in 1985, but by then Conaway was getting a good deal less attention from his public. To help him sleep he began taking Halcion, a prescribed drug that set off erratic behavior in him.
Conaway slipped from public sight going into the 1990s, largely due to his substance abuse problem, though he was a semi-regular (starting the second season) on the sci-fi series Babylon 5, as security officer Zack Allan. He also resurfaced in early 2008 and revealed his troubled past on Celebrity Rehab with Dr. Drew – though he was unsuccessful in staying sober.
In January 2010, Conaway fell down a staircase and suffered a broken hip, a broken arm, a fractured neck and a brain hemorrhage.
Through it all, said his manager, Conaway was a "gentle soul" who simply was not able to "exorcise his demons."