Debbie Martin died at age 61 at a hospital in Escondido, Calif., near San Diego, her husband, Ron Martin, told The Associated Press.
Debbie Martin was the younger sister of Jolie's mother, Marcheline Bertrand, whose own death from ovarian cancer in 2007 inspired the surgery that Jolie described in a May 14 op-ed in the New York Times.
According to her husband, Debbie Martin had the same defective BRCA1 gene that Jolie does, but didn't know it until after her 2004 cancer diagnosis.
"Had we known, we certainly would have done exactly what Angelina did," Ron Martin said in a phone interview.
Debbie Martin's death was first reported by E! News.
Ron Martin said after getting breast cancer, Debbie Martin had her ovaries removed preventively because she was also at very high genetic risk for ovarian cancer, which has killed several women in her family.
The 37-year-old Jolie said in her op-ed that her doctors estimated that she had a 50 percent risk of getting ovarian cancer but an 87 percent risk of breast cancer.
She had her breasts removed first, reducing her likelihood to a mere 5 percent.
She described the three-step surgical process in detail in the op-ed "because I hope that other women can benefit from my experience."
The story, a surprise to most save those closest to Jolie, spurred a broad discussion of genetic testing and pre-emptive surgery.
A message left with representatives seeking comment from Jolie was not immediately returned.