1870 census Plaquemines M593/526 page 217
Kaiger, Catherine - age 42 - farmer - born France
Lafrance, Nicolas - age 20 - farmer - born LA
Lafrance, Pierre - age 14 - farmer - born LA
Elston, Jefferson - age 9
Kaiger, James - age 2
1860 census Plaquemines M653/414 page 729
Ellston, Allen - age 45 - born Kentucky
Ellston, Catherine - age 35 - born France
Lafrance, Marie - age 17 - born LA
Lafrance, Lucie? - age 15 - born LA
Lafrance, Josephine - age 14 - born LA
Ellston, Josephine - age 13 - born LA
Ellston, William - age 10 - born LA
Lafrance, Nicolas - age 9 - born LA
Ellston, Louise - age 6 - born LA
Lafrance, Cecile - age 5 - born LA
Lafrance, Pierre - age 4 - born LA
Ellston, Mathilda - age 9/12 - born LA
Clark, Thomas - age 52 - born Massachusetts - Farm Laborer
Unfortunately, I cannot find them in the 1850 census, where the parents should be with the 3 oldest Lafrance girls.
It may be that Catherine was married to Lafrance first, then Ellston, then Kaiger. Some of these children may be Allen Ellston's children from a previous marriage with the exceptions of Mathilda and Jefferson.
Allen Ellston can be found in 1850 with a wife and no children. Hmmm. Nice mystery here. How can there be Ellston children born before 1850 that do not appear in the 1850 census with Allen, but are in the 1860 census with him?
Hope this helps,