I can tell you a little about this Olivia Brown mentioned. She was born as a slave about 1835 in St. Charles Parish. She died June 16, 1888 in St. John Parish.
When she was a slave she was impregnated by Léo Aimé Becnel and had 3 children: Optimé (b 1858), Henri (b 1860) & Marie (b 1863).
In 1865 she had a child by a Louis Laporte and that child was also named Louis Laporte.
By 1870 she is listed in the St. John Parish Census, Ward 1 (Lucy, La) as Widow Louis Laporte, age 35, mulatto female, children: Optime 12, Henry 8, Marie 7
A few households over is Widow Isaac Jones, 60 mulatto female, Louise Jones 26 female mulatto, Celeste Jones 14 female Mulatto, Louis Laporte b 1870 male, mulatto
In St. John Parish Courthouse you can find the Sale & Transfer of Land by Louis Laporte to Henry Becnel in the succession of Olive Brown, Ins/320 A-14, 132. They are listed as being sons of deceased Olive Brown. This information I received from some descendants of Henri Becnel who I met several years ago while they were doing research here in Louisiana.
Now, Rosette Catherine Laporte was the daughter of Louis Laporte & Catherine Songy. You can find this on their marriage entry at St. John the Baptist Catholic Church, Edgard, La. They were married 24 Jan 1893. Francois was a white man and it appears that Rosette was quadroon. Their marriage took place in the church after the Reconstruction period and after all of their children were grown. Their cohabitation began some 30 years prior.
Catherine Songy was born between 1810-1815. She was listed in the 1870 & 1880 census as mulatto, probably a former slave and child of one of the white Songy men that lived in Lucy. I believe Catherine was also the mother to a Louis Laporte that was born abt 1832 listed as mulatto who latter is listed in the 1880 census with a wife named Roseline and these children: Jules Laporte (b 1864), Odille Laporte (b 1866), Julien Laporte (b 1866), Albert Laporte (b 1871), Alice Laporte (b 1873), Malvina Laporte (b 1876), Alcée Laporte (b 1877), Louise Laporte (b 1880). This Louis could have been a brother to Rosette.
Now who was this Louis Laporte, father of Rosette Laporte? He would have to have been born abt 1810 or well before? Was he the same Louis Laporte that later cohabited with Olivia Brown? Was it the brother of Rosette that cohabited with Olivia? Not enough information is known at this point to make this determination.
There was also a mulatto Olivia Brown listed in St. John & later the St. Charles Census as the daughter of Oliver Brown, mulatto born abt 1816 in Virginia, listed in the census as engineer and husband to Louise Nathalie Ranson (mulatto, native of Louisiana) parents to Olivia b 1849 & Camilla Brown b 1851. This Olivia should not be confused with the slave Olivia b 1835.
If Catherine was listed as a mulatto she was half black/white and Louis Laporte was a white man that means that Rosette was quadroon. Rosette married a white man so that means her children were all 1/8 black or octaroon.
I should also mention, by looking over census records that Catherine Songy was also the mother to a Cecilia Bossier. Cecilia had 5 children by a "Mr Lemoine" - those children were:
Alceste Lemoine b abt 1854 m. Zoe Jagrice
Marie Lemoine b abt 1856
Joseph Lemoine b abt 1858
Josephine Lemoine b abt 1859 m1. Florestan Legaut (Francois' brother)
Louise Lemoine b abt 1863
So this would mean that through Catherine, Rosette's niece married her brother-in-law!
Hopefully we can find more.