http://en.wikipedia.org/wiki/William_Temple_Franklin

William Temple Franklin (London, England, 1760 – Paris, France, May 25, 1823) was the illegitimate, only son of William Franklin (last colonial governor of New Jersey, mother unknown) and grandson of and secretary to Benjamin Franklin. His name derives from the fact that he was conceived while his father was studying at the Middle Temple; indeed, he may have been conceived on Temple grounds.[1]

Temple, as he was familiarly known, accompanied his grandfather to France in late 1776 and worked as secretary to the American diplomatic mission during the American Revolution. Along with his cousin Benjamin Franklin Bache, William received an education in France and Switzerland. A bon vivant, Temple received his highest public appointment as Secretary to the American delegation at the Treaty of Paris in 1782-1783, largely through the influence of his grandfather, but never again attained a significant post. After the elder Franklin died, Temple lived for a while with his father in England, and had an illegitimate child, Ellen (May 15, 1798 London – 1875 Nice, France) with a relative of his father's second wife. He then moved to France, where he won and lost a fortune in real-estate speculation. By a mistress, Blanchette Caillot, he had a son who died young.

As the elder Franklin's literary heir, he edited and published editions of Benjamin Franklin's writings, including his famous Autobiography (London and Philadelphia, 1816-1819).

He married his long-time mistress Hannah Collyer a few months before his 1823 death, in poverty, in Paris, where he is buried at Père Lachaise Cemetery.