Very little is known about Sophia King. Her father was a notorious moneylender named John King (born Jacob Rey in approximately 1753, also called "Jew" King). She and her sister, Charlotte King published a book of poetry together, Trifles of Helicon, and Charlotte also contributed poetry to at least one other book by Sophia. Of the two sisters, Charlotte is the better known and mainly published under the names Rosa Matilda and Charlotte Dacre. The dates of Sophia King's birth and death are unknown, as is the identity of her husband. She did continue to publish after her marriage under the name Sophia Fortnum.