Before he flew to Jordan for King Hussein's funeral, the Prime Minister told BBC Radio 4's Today programme that his late mother, Hazel, had spent years as a carer for his grandmother, Sally Corscaden.
"My mother looked after her mother when she developed senile dementia and all the rest of it," Mr Blair revealed.
"We never thought of ourselves as carers. My mother would have been quite surprised at being given that title. Most people in that position feel the same way about it," he said. It was only in later life, when he started considering the matter in policy terms, that he had realised "there are millions of people out there who are carers, who have huge problems as a result".
For a man who jealously guards the privacy of his family, a stance that led him to report a newspaper to the Press Complaints Commission over a report about his daughter Kathryn's schooling, Mr Blair's remarks may come as a surprise. However, his comments about his mother are just the latest example of prime ministerial candour about the impact on his political thinking of his family background.
In his crucial Labour Party conference speech before the general election he departed from his script to relate how his father Leo's stroke had forced him to abandon his own political career.
With Mr Blair senior sitting in the front row with other members of the family, the Labour leader moved his audience almost to tears with a description of how his character had been shaped by the illness that forced his father, a barrister, to abandon hopes of becoming a Tory MP.
"One morning I woke to be told that he had had a stroke in the middle of the night and might not live through the day, and my whole world fell apart," he said.
The Prime Minister used his experience again last year when he launched a campaign by the Stroke Association for a better deal for sufferers. He was 10 when his father had his stroke at the age of 40. "Stroke often receives far too little attention when compared to the other big killer illnesses," he said. "I know from personal experience it is an enormous problem, which has a profound effect on people's lives."
In March 1997, Mr Blair revealed that an aunt of his wife Cherie had died from breast cancer, as he announced Labour's pledge that no woman would have to wait more than a fortnight for surgery to tackle the disease.
"I know how it can hit a family terribly," he said. "I want to ensure that the NHS will provide the best quality and most appropriate care in these circumstances."
In February 1998, Mr Blair gave his crucial backing to the Millennium Dome with an announcement that its contents would have to pass the "Euan test" and satisfy his 13-year-old son. Dismissing the "cynics and snipers", he said: "I want today's children to take from it an experience so powerful and memories so strong that it gives them that abiding sense of purpose and unity that stays with them through the rest of their lives."Reuse content