I am interested in all (occidental) SENG family history, and am currently working on the "Louisville" Sengs. I've made several contacts and received much info, but not the datum you're looking for. Maybe I can put you in touch with the folks who corresponded with me, but first a question: Could "your" Nicholas Seng be the brother to Kilian Seng who was born in Winnweiler(Rheinbaiern) in 1808 and emigrated to (eventually) the Louisville area? In the listing I have received, Kilian's clan is well documented, but there is only a note that "Kilian had two brothers, Nicholas & Henry," nothing else is provided. Kilian also had a son, Nicholas (b.1848 in KY or So.IND.) who married a Mary Miller (Mueller?) in the 1850's & fathered 10 children with her--his second wife.
If you're sure you N. was born in Baden and not in Rheinbaiern (Pfalz), there is a remote possibility that another family now mostly in the Evansville, IN area might be related. Even if he emigrated from Baden, there is chance that he is a "Louisville Seng."