I checked your posting history to find out more about these men.I saw that you had found Jacob and his family in the 1880 census.
I found them in 1870 as well:
1870 United States Federal Census > Louisiana > West Feliciana > Ward 1 > Page 326
Dwelling 82/Family 103
Jacob Michell, 40, white, grocer retired, b France
Cecile, 27, white, keeps house, b France
Alfred, 5, white, b LA
David, 2, white, b LA
I then checked the 1860 census.There were 2 Jacob Michel(l)s listed.This was the only one of a close age, but I can only guess that it is the same man.
860 United States Federal Census > Louisiana > Pointe Coupee > Page 14
Dwelling 126/Family 139
Nathan Keiron, 34, male, merchant, $2500 property, $2500 land value, b France
Rosine, 34, female, white, b France
Nathan, 7, b LA
Abraham, 5, b LA
Solomon, 4, b LA
Meuyer, 2 months, male, b LA
Jacob Michel, 29, male, b France
I did not see a likely match for Cecile in 1860.
Here is the family in 1900, still in West Feliciana Parish:
1900 United States Federal Census > Louisiana > West Feliciana > St Francisville > District 107 > Page 8B
Dwelling 162/Family 162
Ferdinand St (rents home)
C. Michell, head, white, female, b Mar 1843, 57, Widowed, bore 4 children, all surviving, she and parents b France, immigrated 1850, housekeeper, reads, writes
Maurice, son, b Aug 1873, 26, b LA, father b France, salesman, reads, writes
Arnaud, son, b March 1880, 20, b LA, father b France, salesman, reads, writes
It appears that Jacob has died between 1880 and 1900.You might check with the West Feliciana Parish courthouse to see if they kept death or probate information from that time period.If you can find a death certificate for him, it might list the names of his parents.
Without other identifying information on your remaining relatives, I don't know where to begin looking for them.