Christopher Lawford in September 2005 in Encino, California, while promoting his book, "Symptoms of Withdrawal: A Memory of Clichés and Redemption".(Photo: René Macura / AP)

Christopher Lawford, son of Peter Lawford, nephew of President Kennedy and member of the sprawling Kennedy clan, died at the age of 63.

The news was posted on Twitter by his cousin, human rights activist, Kerry Kennedy, daughter of Robert F. Kennedy.

It was confirmed by Max Burns, a spokesman for Robert F. Kennedy Washington Human Rights Group, led by Kerry Kennedy.

Another cousin, former US representative Patrick Kennedy, told the Associated Press that Lawford died of a heart attack Tuesday in Vancouver, Canada.

"We mourn the loss of my cousin Christopher Lawford, Rest in Peace," tweeted Kennedy, with photos of a Kennedys bus at the 2004 Democratic Convention and Lawford with one of his three children , the son David.

Patrick Kennedy acknowledged that Lawford had helped save him from his own addiction problems.

"With his wife, he was the cornerstone of my sobriety," Patrick Kennedy said Wednesday. "It's him who has guided me through all the difficult days of this early period."

Lawford was the first child of Patricia Kennedy Lawford, sister of JFK and RFK, and Peter Lawford, actor and British member of Frank Sinatra's 1960s cool pack. Lawford's father died in 1984 ; his mother in 2006.

Lawford has been married three times and has survived three children from his first marriage and his third wife, Mercedes Miller, a yoga teacher, whom he married in 2014.

Christopher Kennedy Lawford, who was very much like his father, was born in Santa Monica, California, in 1955, the only son of his parents' four children.

, Christopher Lawford in September 2012 in Beverly Hills, California. (Photo: Todd Williamson / Invision / AP)

It was an actor with a long list of credits, but perhaps best known for his roles on soap operas "General Hospital" and "All My Children" and a role in one of the films "Terminator" featuring his handsome -cousin, Arnold Schwarzenegger.

He also wrote a dissertation on withdrawal symptoms in 2005: "Withdrawal Symptoms: A Snapshot and Redemption Memoir," about his near-fatal addiction to alcohol, opioids, and drug abuse. # 39; heroin.

He also published another book in 2009, "Moments of Clarity: Voices from the Front Lines of Addiction and Recovery," a collection of essays from different celebrities on their addiction issues.

As a political activist, Lawford has worked on many political campaigns in Kennedy, including those of his uncle, the late Massachusetts senator Ted Kennedy.

A graduate of Tufts University in Massachusetts and Boston College Law School, he earned a master's degree in clinical psychology from Harvard University where he obtained an academic position as a lecturer in psychiatry.

Lawford fought a substance abuse problem from the late 1970s to the early 1980s, becoming a heroin addict. In 1980, he was arrested in Aspen, Colorado, for spoofing the identity of a doctor in order to obtain prescription drugs. The charges were dropped later when Lawford completed his probationary period.

He was inspired to get rid of his drug after April 1984, when his cousin David, another son of Robert F. Kennedy, died of a drug overdose. Later, Lawford helped set up a clinic to treat opioid addiction in Boston.

Contributor: Associated Press

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