William MANG married to Justina KOCH. They seemed to immigrate to the US via NY. and settled in NYC before coming straight to Buffalo. William MANG was naturalized around 1850. They lived at 51 East Tupper which is in Old East Side. I can't find a Louis MANG in my family but then again I have not worked on the descending lines. The name ISADORE seems to lead me to believe that it is a family name and crops up quite frequently in the Frank MANG family connections.
I am really trying to find more. But I am not really looking at descending lines. You may have to work back a bit further to see where your connection may be. I would say you would only have to go back another generation to see which MANG family of Erie County that you descend from. Go to your local Family History Center ( run by the Mormon Churches and you will be able to see films of City Directories and Census records to find your family and make a connection. ) Let me know how you make out. You can contact me directly at: email@example.com
There is another MANG line that is being researched by Robert BALL of Michigan. The Kenmore MANG family - descended from Pierre MANG and Margarethe RAME. But my direct line of Buffalo does not tie into this family. Maybe yours does. I will send you Robert's addresses and you can contact him directly to see if there is a connection to his family.
Isadore Eugene is ason of Frank MANG. He was born Dec. 1871 Also a sibling of Frank MANG is listed as Isadore born circa 1833 - confirmed at St. Pierre's RCC in Buffalo. All of these folks are descended from Jean Pierre MANG and Margarethe RAME.