My paternal grandmother, Meena (Meacham-526) (her real name was Lillian Florence, but she was always known as Meena, short for Wilhelmina, because, as a child, she was thought to resemble (then) Princess (later Queen) Wilhelmina of the Netherlands) was married 3 times, and had at least one long-term extramarital relationship.
In 1908, as a piano student at the Royal Academy of Music in London, she married the musician, and collector of Irish folk songs, Herbert Hughes. Later that year they had a son, Patrick (later known as Spike) Hughes. But by 1911 they were living separately.
By 1914 she was living with my grandfather, an Egyptologist, Battiscombe (known as Jack) Gunn. But she was not divorced from Herbert until 1922, when he wanted to re-marry, and she didn't marry Jack until about 1926. Their marriage was registered in Beirut, Lebanon. My father, Iain, was born, in Cairo, Egypt, in 1928.
Dyring WW II my father was evacuated to the US to stay with some family friends, until the dangr of bombing in England was thought to be passed. When he returned to England he was surprised to dicover that his parents had divorced, and his mother had married Alex Grey-Carke, a neurologist 30 years younger than her (younger than her first son, Pat). Nobody had told him anything about it, and I have a Christmas letter (dated after the divorce and Meena's remarraige) that Meena and Jack sent, and signed jointly, as if nothing had changed.
Alex died a few years later, in 1944, of meningitis, acquired during his survival of the sinking of H.M.S Courageous, which was torpedoed by a German U-Boat on 17 September 1939.
I never knew any of her husbands (they all died before I was born), but I knew Meena quite well.
One of my high school colleagues who knew her said Meena was the "first liberated woman I have met".
(Added 3 hours later)
In addition to her marraiges, she had a long lasting (over 3 decades) reationship with the brilliant (but now sexually notorious) sculptor and font creator (e.g. Gill Sans) Eric Gill ( https://en.wikipedia.org/wiki/Eric_Gill ). He was one of the few people who called her Lillian instead of Meena. In 1907 (when Gill was married, but Meena was not yet married to Herbert), they spent a "romantic tryst" over the long Easter weekend, in Paris and Chartres, attending the Paris opera, visiting Chartres cathederal, and reading Nietsche and Theosophical papers.
Their relationship continued, with varying degrees of intimancy, until Gill's death from lung cancer in 1940. Meena's first son, Pat, fondly remembers (in his autobiography) spending summers with Meena and Jack in a rented cottage in Ditchling, where Gill had what would now be called an artistic commune, from 1918 to 1924.
Meena's sister, Wendy Wood, in her autobigrapy, remembers baysitting Eric Gil's children during the early 20th century.
Gill also dedicated a phallic sculpture to Lillian (decades after their first encounter in 1907).