Robert F. Kennedy's daughter Kerry mourned Christopher Lawford's death on Twitter
20th Annual Friendly House Luncheon
Credit: Angela Weiss/Getty

Christopher Lawford, an actor who was one of John F. Kennedy’s nephews, has died. He was 63.

Lawford’s cousin Kerry Kennedy, who is the daughter of Robert F. Kennedy, confirmed the news on Twitter Wednesday.

“We mourn the loss of my cousin Christopher Lawford, Rest in Peace,” she wrote along with photos of Lawford at the 2004 Democratic Convention with son David.

Patrick Kennedy, who revealed on Twitter that Lawford suffered a heart attack, also told the Associated Press that Lawford died in Vancouver, Canada, on Tuesday.

Christopher’s father Peter died of a heart attack after being hospitalized for alcohol-related liver and kidney problems in 1984.

In addition to his prominent lineage, Lawford was best known for his acting career, with TV roles on shows including General Hospital, All My Children and Frasier, as well as film roles such as 2003’s Terminator 3: Rise of the Machines.

In his 2016 book, When Your Partner Has an Addiction: How Compassion Can Transform Your Relationship (And Heal You Both in the Process), Lawford opened up about his addiction to LSD, which he said started at age 14 and ended at age 30 when he went to rehab. He attributed his issues to his parents’ bitter divorce and the assassinations of his uncles John and Robert.

Kennedys Arriving For Mass
Christopher Lawford with John F. Kennedy
| Credit: Getty

“I had friends trying to get me to use LSD in seventh grade. I grew up with an ethic of trying to do good in the world, and I said no. Then my Uncle Bobby was shot. Next fall they asked me again and I said sure,” Lawford wrote, according to the Chicago Sun-Times.

After graduating from Tufts University in 1977, Lawson enrolled at Fordham Law School but had developed a heroin habit that forced him to drop out only a few months later. Seven years later, in 1984, his cousin David Kennedy, the fourth of eleven children of RFK and Ethel Skakel, died of a drug overdose at age 28.

“David and I were just best buddies. It’s really hard when you lose someone you care about,” Lawson told PEOPLE in 1991, adding that David’s death helped fuel his determination to complete his own recovery.

“I never expected to make it to 30,” he said at the time. “I shouldn’t have. I just have to stay out of my own way, because I’ve got this capacity to screw things up.”

In 2006, Lawson released the memoir Symptoms of Revival: A Memoir of Snapshots and Redemption, in which he recalled memories such as getting dance lessons from Marilyn Monroe, watching Judy Garland play poker, and hanging out with Rat Pack members Dean Martin, Sammy Davis and Joey Bishop.

“There are many days when I wish I could take back and use (my youth) more appropriately. But all of that got me here. I can’t ask for some of my life to be changed and still extract the understanding and the life that I have today, with my children, with my friends, with my lover. All of those relationships are the result of all that I have gone through with my life,” Lawford told the Today show at the time.

Lawford is survived by his children David, Savannah and Matt as well as his sisters, Sydney, Victoria, and Robin.