The story of how an alcoholic Irish butler inherited a $5m fortune is to take centre-stage at the prestigious Emmy Awards in the US tonight.

A film about Donegal man Bernard Lafferty's relationship with billionaire Doris Duke has been nominated for 10 awards at the ceremony.

However, the HBO drama Bernard and Doris, which stars Ralph Fiennes and Susan Sarandon, is at the centre of controversy after objections by Lafferty's remaining family in Donegal. Speaking from Crees-lough, Donegal, Lafferty's cousin, also called Bernard Lafferty, says he has seen the film but doubts its accuracy.

"It's like any film – some of it's true and the rest is fiction. But Ralph Fiennes is a brilliant actor and is very good in it."

Director Bob Balaban, who also directed Capote and Gosford Park, has defended the screenplay by Irish writer Hugh Costello, stressing it is a work of fiction.

"We took a lot of liberties to create a film that would be emotionally and dramatically satisfying. This isn't a factually accurate account of Duke's life."

Made on a shoestring budget of $500,000, with Sarandon and Fiennes waiving their usual Hollywood fees, the film was greeted with rave reviews when it aired on US cable channel HBO in February.

This is not the first film to be made about the eccentric butler; Hollywood has been long fascinated by the relationship between the lavish tobacco heiress and her Irish servant – the 1999 mini-series Too Rich: The Secret Life of Doris Duke featured Lauren Bacall and Richard Chamberlain as the two lead characters.

Both RTÉ and ITV have shown documentaries describing the Creeslough man's rise to fortune. Tobacco heiress Duke was made a billionaire following the death of her father in 1925. Just 12 years old at the time, she was dubbed "the richest little girl in the world".

In the years before her death, she was named in the Forbes rich list as the 18th richest woman in the US.

By contrast, Lafferty had more humble beginnings. He emigrated from Co Donegal to the US following the death of his parents and worked for the singer Peggy Lee before joining Duke.

He became a close friend to the billionaire, becoming her only confidant in the last few years of her life.

But Lafferty provoked suspicion. He was reportedly a binge-drinking alcoholic who also took a dangerous cocktail of prescription medication and seemed bent on isolating his increasingly frail employer.

In her last years, Duke rewrote her will six times. When she died aged 80 in 1993, Lafferty was made executor of her $2.5bn estate to everyone's disbelief.

He also stood to make $5m in executor fees and an annual payment of $500,000 for life. In the 12 months that followed, he ran up credit-card bills of nearly $155,000 at luxury stores and spent $60,000 to renovate Duke's old bedroom for himself.

Suspicion surrounded him when it was revealed that he had had Duke's remains cremated within hours of her death. A staff member accused Lafferty of having drugged Duke with morphine, but a police investigation found no evidence to support this.

A court case ensued and Lafferty lost control of his fortune, only to have it reinstated the following year.

He did not get to enjoy his wealth for long as he died months later in November 1996.