Ellis Agar Hartley's origins are interesting but confusing. In Burke's History of the Colonial Gentry, published in 1891, in Volume I page 192, it is recorded that the Countess of Brandon was her
godmother. However, in Volume II amongst the corrections, on page xxi, it is mentioned that the Countess of Brandon was her mother, not her godmother, and that her father was King George IV.
In the Gentleman's Magazine, we find the Countess of Brandon, nee Ellis Agar, to be described as having "genuine wit, elegance of taste, dignity of manners, and superior understanding" and, in the Complete Peerage, it is mentioned that she was born about 1708, had been married twice, and on 15 September 1758, eight years after the death of her second husband, King George II created her Countess of Brandon for life and, on 11 March 1789, she died childless.
King George IV was born in 1762, which makes the Countess of Brandon his senior in age by about fifty-four years. No dates are given for the birth of Ellis Agar Hartley, but Charles Ryan, probably her eldest child, was born in 1818. If the Countess of Brandon was Ellis Agar Hartley's godmother, then she must have been born before 11 March 1789, which makes Ellis Agar Hartley close to thirty in 1818. As it was not customary for the Hanoverian Kings to acknowledge their
illegitmate offspring, it seems likely that King George IV was the father of Ellis Agar Hartley, but who was her mother? Taking into account her name, Ellis Agar Hartley, and the name of the Countess of Brandon, Ellis Agar, it seems likely that there was indeed a link, not mother and daughter, but more likely great-aunt and great-niece or even grandmother and granddaughter.
 

Source: Leo van de Pas