Vincent Lambert, the man at the centre of a years-long life-support battle that played out right up until his death on Thursday, was the silent witness to the wrenching public feud between his parents and wife.

Lambert was a rebellious teenager who had settled down and was due to become a father when was in a devastating car crash in 2008 that left him in a vegetative state.

With doctors declaring his condition irreversible, his future became the subject of a bitter legal battle between his deeply Catholic parents, who fought tooth and nail to keep him alive, and his wife and doctors, who argued that the more humane option was to let him die.

In the end, his wife Rachel and the medical team at Reims University Hospital prevailed, with doctors taking him off life support on July 2 after France's top court ruled that doctors could remove his feeding tubes.

His eight siblings were drawn into the tussle, with six of them backing his wife, and two others supporting his elderly parents in a struggle over passive euthanasia that made headlines around the world.

"He is minimally conscious but he is not a vegetable," his 73-year-old mother Viviane pleaded in a last-ditch appeal on Monday before the UN's top rights body in Geneva.

But for his wife, the fight was about what Lambert himself would want: "Keeping him artificially alive and totally dependent? For him, that would be unacceptable," she has said.

Before the accident, Lambert was a thrill-seeker who loved to party and was once expelled from school, family members told AFP.

"He sometimes went to extremes, but at the same time he was secretive, withdrawn and ill-at-ease," younger sister Marie once said in an interview with AFP.

- Strict Catholic upbringing -

Viviane and Pierre Lambert are devout Catholics who have a total of nine children between them / © AFP/File

He was the first child born to Viviane and Pierre Lambert, who each had children from a previous marriage.

When his parents met, his father was a gynaecologist and active anti-abortion campaigner, who had two children before falling for Vivianne, who was his secretary at the time.

She was a mother-of-three and 16 years his junior.

The pair eventually got married and went on to have four children of their own, with Vincent the sixth out of a total of nine children.

Like the rest of his siblings, Lambert was sent at 12 to a strict Catholic boarding school in southwest France, but was thrown out for insubordination. He went on to finish his studies in the northwestern city of Reims.

"Since then he always distanced himself from our parents' ideology, like most of us," Marie said.

After school, he studied nursing specialising in psychiatry, which took him to various hospitals in the region where he met Rachel, also a nurse. They married in 2007.

But barely 18 months later, while Rachel was heavily pregnant with their daughter, Lambert crashed his car in Chalons-en-Champagne where they were living.

- Kept in a locked room -

Vincent Lambert's wife Rachel says "because I love him, I want to let him go" / © AFP/File

He was rushed to Reims hospital, where he remained until his death, behind a locked door with a camera keeping a close eye on visitors.

Over the years, his family watched as his condition deteriorated, his muscles wasting away, a grimace becoming etched on his face, the occasional cry.

Although he has been known to smile or shed tears, experts believe it to be the result of "emotional memory" rather than a real-time reaction to events.

His 73-year-old mother, and his father, 90, had threatened to bring murder charges against the doctor that removed his feeding and hydration tubes.

"Vincent is doing well. He's not at the end of his life," his mother said in May. "He only needs something to drink and to eat and some love."

His 38-year-old wife, who moved to Belgium with her 11-year-old daughter to escape the media attention over the case, has written a book about her experience, entitled: "Because I love him, I want to let him go."