I am also researching the "Kostmayer" family of New ORleans and MS and Alabama. My son in law is a Kostmayer and I finally got genforum to set a sight for this name. Here is part of info I have so far.
Thiabaut E. Kostmayer married Catherine Bauregard b:1854 d:June 10,1921 New Orleans,LA ISSUE: 1. Thiabaut Paul (T.P.) Kostmayer b:May 10,1873 m: Caroline Hertzer and had John George d:3-10-1934 NO,LA 2. Catherine Kostmayer b: 8-26-1877d: 2-23-1878 NO,LA 3. Charles Robert Kostmayer b: 12-9-1880 NO,LA 4. John Henry Kostmayer b: 2-12-1883 NO,LA 5. Florence Angell Kostmayer b: 6-11-1886 d:11-8-1902 NO,LA 6. Allen Kostmayer b: 1-25-1888 NO,LA 7. Samuel E Kostmayer b: 12-25-1890 NO,LA this is the line that I am researching.
Would love to share info with anyone on this family tree.