I believe the Ernest Lightell you mention was born about 1860. His wife, Athanasie (Martineice/Aniece)Barthelemy was born about 1860. Corinne Andry was her mother, Barthelemy Baptiste-Barthelemy her father. When young, Baptiste, after 1850's, Barthelemy. Ernest's parents were Jacques Lightell, born about 1822, and Mary Ancar. Mary was the second wife, daughter of Charles Ancar and Lucy DeMolle. Jacques' parents were James Lightell and Marie Rose Baptiste. Charles was 3/8 Indian, born 1790. Marie Rose Baptiste was 3/8 Indian, 1/16 other colored, born 1797. Charles and Marie Rose Baptiste were cousins, his mother, her father were double first cousins. The slave ancestry was before 1750, three different routes.
The Andry family came to Plaquemines Parish shortly before 1850, and were free colored. Bart seems unclear, since two were born between 1834-37 time period. One was the son of Jacques Barthelemy-Baptiste and Francoise Barrat. The other was the son of Barthelemy Baptiste, Jr. and Brigitte St.Ann. Since the 1837 Bart had a sibling, Adelaide, who married Noel Andry, I believe the Barthelemy and Brigitte couple was yours. Jacques and Barthelemy were brothers, and Marie Rose Baptiste their sister. Their parents were Barthelemy Baptiste(1762 - 1844) and Catherine Lafrance. Barthelemy was 3/4 Indian, Catherine 1/8 other colored. Brigitte St. Ann was daughter of Carlos Santana and Marie Therese Baptiste, and cousin of Charles Ancar. Their mothers were sisters. Therese's sister Genevieve and Francois Ancar dit L'Abbe' were Charles' parents. Carlos Santana came from Santiago de los Cabaleros, Santo Domingo. Since Carlos was colored, he could marry Therese. Francois was white, so he was not married, but had many acknowledged children with Genevieve.
The racial term mulatto, came about since the family was about 1/2 colored at one point. In Louisiana, if an Indian were made a slave at one point, upon freedom, that individual would become a free person of color, with the non European ratio falling into the Black system(Negro, Griffe(3/4), Mulatto, Quadroon, etc.) Griffe fell out rather early, and mulatto stuck for most who fell between quadroon and "full black."
Hope I didn't confuse you with the twists in the root. Common down here. Richard