Hi Morris -
I am a descendent of Francois and this is a bit of info we don't have, so that you so much for posting it.
Dr. John Chastang was one of Francois' sons, Joseph (my lineage) the other. Dr. John and Joseph both were born to Francois and his wife, Marie. It was Dr. John that married a slave. She belonged to Joseph and Dr. John gave her the money to buy her freedon and the freedom of 4 of their children. They were later married and had 6 more children, one of which was named Francois.
Dr. John was responsible for a few quite remarkable things in that day and time.