Mary Shelley's stepsister, mother of Byron's daughter (1798–1879)
Clara Mary Jane Clairmont (27 April 1798 – 19 March 1879), or Claire Clairmont as she was commonly known, was the stepsister of English writer Mary Shelley and the mother of Lord Byron's daughter Allegra. She is thought to be the subject of a poem by Percy Bysshe Shelley. Early life. Clairmont was born in 1798 in Brislington, near Bristol, England, the second child and only daughter of Mary Jane Vial Clairmont. Throughout her childhood, she was known as Jane.
https://en.wikipedia.org/wiki/Claire_Clairmont