The latest show from Peaky Blinders creator Steven Knight tells the thrilling story of brewing dynasty the Guinnesses – and was devised by Guinness descendant Ivana Lowell, laying bare her ancestors' rivalries, scandals, secrets and tragedies.

Ivana Lowell was in Ireland for a family gathering at Castletown, the Palladian mansion restored by her cousin Desmond Guinness in County Kildare, when inspiration struck. She and others were watching, in a desultory way, an episode of Downton Abbey on television. The sight of the fictional Crawleys throwing polite barbs at each other across the dining table made Lowell realise something. "Our family history was a lot juicier and more interesting than this – plus it was all true," she tells the BBC from her airy East Hampton dining room.

When she returned home to Long Island in New York, she sat down and wrote a 20-page television treatment, a dramatic retelling of the triumphs and travails of her clan, descendants of Arthur Guinness (born 1725), who first brewed the famous Irish stout beer which now sells over 10 million glasses a day around the world. Fast-forward a decade, and Lowell's concept has been brought to life by the acclaimed TV writer and director Steven Knight, best known for Peaky Blinders. Eight episodes of House of Guinness will drop on Netflix on 25 September, with a prominent call-out in the credits: "Based on an idea by Ivana Lowell."

Lowell – whose mother was the novelist Lady Caroline Blackwood, and whose grandmother, Maureen, Marchioness of Dufferin and Ava, was one of the trio of "golden Guinness girls", well-known in British high society in the 1920s – concedes that the epic story wasn't a simple one to tell. It sprawls over six generations and involves remarkable commercial success, a rich philanthropic legacy plus political intriguing, along with numerous family rivalries, scandals, secrets and tragedies.

She began her treatment by addressing the mythical origin story of Guinness dark stout, as an accidental burning of the hops. In truth, founder Arthur most likely landed upon with his winning stout formula deliberately, allowing darker malt beer to mature in wooden vats, deepening its flavor.

For the TV series, Knight plucked from Lowell's storyline a later kick-off point: the death of Benjamin Guinness, the founder's grandson, who died in 1868, leaving behind four children. He'd built the brewery established by Arthur at St James Gate in Dublin into one of the largest in the world, and the Guinness family counted among Ireland's wealthiest citizens.

The plot will remind some viewers of Succession, the HBO hit loosely based on media mogul Rupert Murdoch's relationship with his four oldest children. As in that tale, wealthy progeny jockey amongst themselves, but in House of Guinness the heirs must cope with the posthumous wishes of their patriarch, plus conditions in 19th-Century Ireland – a vocal temperance movement and political tumult fuelled by the dominance of the prosperous Protestant elite, to which the family belonged, over the impoverished Catholic majority.

"They were all so young, and their father left them both huge responsibility and a huge legacy," Lowell says of her four main characters. "Each was forced to find a path." As a woman, Anne, the sole daughter, inherited only a nominal amount, but committed herself to tapping family funds to improve the lives of the poor and sick in Dublin,........

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