Debbie Martin, 61, died in a hospital in Escondido, near San Diego, California, according to her husband, Ron. She was the younger sister of Jolie's mother, Marcheline Bertrand, whose death from ovarian cancer in 2007 prompted the actor to have the surgery she described in a New York Times article this month.
Jolie revealed that she had a defective gene, BRCA1, which significantly increased her risk of developing breast and ovarian cancer. "Once I knew that this was my reality, I decided to be proactive and to minimise the risk," she wrote.
Ron Martin said his wife also carried the gene but had not been not aware of it until she was diagnosed with cancer in 2004. "Had we known, we certainly would have done exactly what Angelina did," he told Associated Press.
He added that after developing breast cancer, his wife had her ovaries removed to minimise her chances of the disease returning.
In the New York Times article, published on 14 May, Jolie explained how her mother's death had informed her decision to have surgery. "My mother fought cancer for almost a decade and died at 56," she wrote. "She held out long enough to meet the first of her grandchildren and to hold them in her arms. But my other children will never have the chance to know her and experience how loving and gracious she was."
The actor said her children had asked her if she, too, was likely to suffer the same fate. "I have always told them not to worry, but the truth is I carry a 'faulty' gene, BRCA1, which sharply increases my risk of developing breast cancer and ovarian cancer," she wrote.
On being told by doctors that she had an 87% risk of breast cancer and a 50% risk of ovarian cancer, she decided to undergo three months of operations.
The 37-year-old, who has six children, finished three months of medical procedures on 27 April. She said she first had "nipple delay" to maximise the chances of saving her nipples, before breast tissue removal and, nine weeks later, reconstruction. Her husband, Brad Pitt, was by her side for "every minute of the surgeries", she added.
Jolie with her mother, Marcheline Bertrand, left, and actor Jaqueline Bisset in 2001. Photograph: Kevork Djansezian/APJolie said she decided to go public in the hope that other women would benefit from her experience. "I wanted to write this to tell other women that the decision to have a mastectomy was not easy," she said. "But it is one I am very happy that I made. My chances of developing breast cancer have dropped from 87% to under 5%. I can tell my children that they don't need to fear they will lose me to breast cancer."
She said it had been reassuring to see that her children had not been made uncomfortable by the process. "They can see my small scars and that's it," she wrote. "Everything else is just Mommy, the same as she always was."
Jolie's decision to share her experiences was widely praised. Wendy Watson, founder of the UK's National Hereditary Breast Cancer Helpline, said the article had helped to focus attention on the issue. "It is excellent, because it is the highest profile you can get for it," she said. "It raises the profile for other women to look to if they have a family history and would benefit from being screened more frequently, or having surgery or having a genetic test.
"She probably feels that undergoing the operation is common sense but it probably does take a certain amount of courage to face it."