|By Peter Lely via Wikimedia Commons|
Catherine grew up in an unhappy home. Her father, the poet Sir Charles Sedley, was renowned for enjoying the lascivious social life of Restoration England, while her mother went insane, insisting that she was the Queen, and was eventually put away in a hospital. The teenaged Catherine found herself on her own when her dad brought a new ladylove into the home. Somehow, Catherine landed on her feet with a position in service to Princess Mary of Modena, the new wife of James (then Duke of York.) This brought her to the Duke's amorous attention. After his accession, he created her Countess of Dorchester. She remained in England after he was forced from the throne in the Glorious Revolution of 1688, although she was not immediately admitted back at court, eventually earning a pension from King William III. A few years later, she married David Colyear, who would later become Earl of Portmore.
Catherine and James had several children, but only a daughter, Catherine Darnley, survived. From her descended the celebrated Mitford sisters. Through one of her sons by her husband, Catherine Sedley is the ancestress of Charles Darwin.
Renowned for her wit and her biting honesty, she told her sons by Portmore, "If anybody call either of you a son a whore, you must bear it; for you are so: but if they call you bastards, fight till you die; for you are an honest man's sons."
For more about Catherine, I recommend Royal Mistresses: Catherine Sedley, Countess of Dorchester on the Scandalous Women blog, which I consulted for this post.