Your great grand father's brother's name was probably Emile and not Emilie. Emilie is usually a girl's name corresponding to Emily in English. Emile in french is pronounced as if the e at the end does not exist, but in english is very often mispronounced somehowlike Emily. Is it also possible that your grand father's first name be Abélard?
Paul-Emile François, my great grand father was born in the 1830's but died in Port-au-Prince in the 1930's. Jacmel where he was perhaps born is on the south coast of Haiti and a more propitious base from which to trade with the Virgin Islands and PR than other cities of Haiti. One important point to note is that the Dominican Republic was from 1795 to 1821 a french territory and from 1822 to 1844 part of the Republic of Haïti. It is conceivable that some François were based there too at one time.
There was a Louis Francois mentioned on page 145 of volume 5 of the Histoire d'Haïti by Thomas Madiou. He was chief of the 18th bataillon of the republican forces of Alexandre Pétion in an 1812 defense of Port-au-Prince against a major assault by the troops of King Henry Christophe.
There was also a Jean-Louis François also a military officer in many battles leading to the independence of Haiti
But François is a very common name in French. If we look for Emile François in France, 38 are found listed in the Phone book. http://fr.people.yahoo.com/py/psPhoneSearch.py?FirstName=Emile&LastName=Fran%E7ois&City=&PostalCode=&srch=residenthttp://fr.people.yahoo.com/py/psPhoneSearch.py?FirstName=Emile&LastName=Fran%E7ois&City=&PostalCode=&srch=resident For François with a first name containing Louis 166 are found. Haiti is probably your best bet and perhaps Jacmel if they were born there. If you have pictures of your ancestors, that may help finding resemblances and better direct your search.
I wish you luck in your search. I will keep you in mind if I find anything.