24-year-old Caitlin Leggett from Cardiff, Wales, was diagnosed with terminal cancer and was told she had “six months to live.” Sadly, she died only a month later. At the hospital, she found out that she and her sister, Grace, were identical twins. It turned out, Grace was ineligible to donate stem cells because their DNA was nearly identical.

In April 2025, Caitlin Leggett, 24, from Cardiff, Wales got the terrifying news. She was diagnosed with acute myeloid leukaemia, an aggressive white blood cell cancer. She went into remission after undergoing chemotherapy and later had stem cell transplant. However, in May this year, the cancer had returned.

As treatment options in the UK was unlikelty to be curative, her family raised money for a transplant overseas. Her twin sister, Grace, wrote on GoFundMe, “We have just celebrated our 24th birthday, and without urgent overseas medical treatments, it will be her last.

She continued, “Caitlin’s only chance of a cure is to raise funds to support overseas medical treatment.”

Grace and Caitlin were not only sisters, but also best friends. As reported by the BBC, they had always been cose and even lived together at university. It wasn’t until after Caitlin’s diagnosis they discovered they were identical twins.

For years, everyone believed Caitlin and Grace were fraternal twins because they had developed in separate amniotic sacs. But when doctors began evaluating Grace as a potential stem cell donor for her sister, they made a stunning discovery, the BBC wrote.

Identical twin Caitlin Leggett died 1 month after given ‘6 months to live’
Tests revealed that the twins shared exactly the same genetic markers – meaning they were, in fact, identical twins. While it came as a surprise, it also was heartbreaking news. Because of their nearly identical DNA, Grace was no longer able to donate her stem cells to help save her sister.

“We’re only 24 – nobody expects this to happen… Being twins as well, you’re not supposed to have one twin not be there,” Grace told the BBC.

Caitlin added, “It’s unthinkable. We’ve gone through life together and I don’t want our story to end here.”

On June 16, Grace shared the heartbreaking news that her twin sister, Caitlin Leggett, had passed away the day before. She had suffered a “brain bleed” alongside other health complications.

“We regret to inform you that in the last few days, Caitlin experienced a sudden and serious brain bleed, followed by a series of strokes which led to a rapid decline in her health,” Grace wrote on GoFundMe.

“Surrounded by the love and care of her family, Caitlin passed away peacefully…We appreciate your love and support during this difficult time.”

Rest in peace, Caitlin. Our thoughts and prayers go out to her family.