Amelia Osborne, Marchioness of Carmarthen

Amelia Osborne, Marchioness of Carmarthen, 12th Baroness Darcy de Knayth, 9th Baroness Conyers, 5th Countess of Mértola ("née" Darcy; 12 October 1754 – 27 January 1784), was a British peer and a Portuguese countess.
Life.
She was the only surviving child of Robert Darcy, 4th Earl of Holderness, and his wife, the former Mary Doublet. Her portrait was painted in about 1764 by François-Hubert Drouais. On 29 November 1773, she married Francis Osborne, Marquess of Carmarthen, in London, and they had three children:
In early 1777 Amelia's mother Lady Holderness broke off relations with her daughter after the Camarthens gave shelter to Richard Glover (son of the poet), a friend of Lord Camarthen, when he eloped with one of the daughters of Solomon Dayrolles.
On 16 May 1778, as the only surviving child of her father, Amelia succeeded "de jure" to the titles of 12th Baroness Darcy de Knayth and 9th Baroness Conyers in her own right, and to the Portuguese countship of Mértola. Her right to the baronies of Darcy de Knayth and Conyers was eventually confirmed in 1798, long after her death.
In December 1778 Lady Camarthen's marriage ended when she ran off with Captain John "Mad Jack" Byron. Byron had been visiting her at home in Grosvenor Square when her husband was absent, and they had been having an affair. Lord and Lady Carmarthen were divorced on 31 May 1779. Almost immediately after the divorce, she married Byron. They had three children:
A year after the birth of last child, Amelia died and the titles were inherited by her eldest son, George. By his second wife, her widower became the father of the poet, Lord Byron.