For years, Hemingway ignored the drinking, addiction and mental illness that coursed through her family, leading several relatives to take their own lives.
Her grandfather Ernest Hemingway, the Nobel Prize-winning writer, killed himself in 1961 just months before she born. Mirroring his own father's suicide, he shot himself.
One of her sisters, Margaux, died of an overdose in 1996 at the age of 42, and her youngest sister, Joan, has been in and out of institutions for a decade.
Mariel Hemingway, 51, who soared to fame in her Oscar-nominated role in the Woody Allen film "Manhattan", has faced her own demons, battling depression.
But she hopes that talking opening about the so-called Hemingway curse in a new documentary, "Running from Crazy", will help others confront mental illness in their own families.
"I never felt it was a curse but I definitely wanted a normal life," Hemingway told Reuters in London on Wednesday where she attended the opening night of "Fiesta", a play based on Ernest Hemingway's first novel, "The Sun Also Rises".
"There are lifestyle choices you can make which can change the course of your life. I have been able to do that through the food I eat, what I drink, what I do on a day-to-day basis. I have managed to find a balance."
The documentary, which made its premiere at last month's Sundance Film Festival and is due to be released in Britain this spring, explores her parents' tumultuous marriage and her troubled relationships with her siblings.
It includes footage of her sister Margaux, a model and actress, whose death she refused to say was suicide until 2003.
"Making this documentary ended up being very therapeutic," she said. "It was not until recently that I realised I had been depressed for so long and I am finally happy."
Hemingway said her family and her own battles had made her passionate about advocating awareness about suicide and mental illness with her own two daughters as well as other people.
"Mental illness especially in the United States is still taboo. Hopefully seeing what my family has gone through will help people talk about these issues," she said.
Hemingway said she was currently working on turning her grandfather's posthumous memoir "A Moveable Feast" into a film and was acutely aware how difficult it was to adapt his prose, which was so often dependent on what was not said.
"You have to have a very delicate hand to adapt his work," she said, praising "Fiesta", which was adapted from "The Sun Also Rises" and directed by Alex Helfrecht.
Helfrecht received approval from the Hemingway estate to adapt the novel, which follows a group of hard-drinking expatriates from Paris to Pamplona's bull-running festival in the 1920s, for the stage. "Fiesta" runs at the Trafalgar Studios 2 until March 2.
(Reporting by Belinda Goldsmith; Editing by Angus MacSwan)