It is suspected all three family members died from the same condition, with their surviving relatives set to be tested on whether they are at risk.
Ashley's devastated dad has told ChronicleLive how he believes his daughter died of a broken heart.
"It is the same as what happened to Jak. The main artery has ruptured. The coroner has said it is like a broken heart. She has been devastated since Jak died," Keith Tomkin said.
He said the family is coming to terms with the third unimaginable loss in just a few weeks, with Ashley having died in the early hours of Monday morning while at home with her mum Jill.
Jill heard her daughter go to the bathroom during the early hours of Monday and when she went in, she found Ashley having a seizure.
Jill called an ambulance, but there was nothing paramedics could do to save the 32-year-old's life.
Tomlin added: "They had a quiet night in and it got to about midnight, when Ashley went to the bathroom.
"Jill heard a noise and when she went in, she found Ashley having a seizure. The paramedics couldn't bring her round.
"They think it was a massive heart attack, but I have my first meeting with the coroner and he told me he wishes they could put 'broken heart' on the death certificate, because that is basically what it was."
Previously, their son Jak underwent surgery when he was just three months old after being diagnosed with a hole in his heart.
Despite his condition, Jak was a keen footballer, playing goalkeeper for his school team and was a regular at South Shields Football Club's weekly training sessions.
After dealing with the loss of his father and grandson, Keith was in Azerbaijan when he received the news about his daughter's death.
He added: "Ashley was our only child. I've lost almost my whole family in a matter of four weeks. Jill has lost the main focus of her life. They were her life.