This is wonderful information! Thank you!
I do not believe that Lena is a "wild goose" chase. I have spent the last two days on familysearch.org and using that data together with data I already had, I am convinced that Lena was Wilhalm's (William's) sister.
Looking at deed records from Williamson county, you can find that William and Henry C. Hartmann not only had adjoining farms in the Noack community, but they bought and sold other plots of land together.
Since William's wife Bertha was HC's sister this "togetherness" was not unusual. But, to have William and Lena be brother and sister adds a greater dimension to these family linkages.
Since Lena was a servant in the Industry, TX blacksmith family, it would be easy to see how a relationship with HC would develop.
I also found Lena's immigration information. Both she and another sister, Minna, came to the US on the ship Strassburg to New Orleans in Nov 1878. They are listed with last name of "Binger" - another phonetic spelling of the family name.
I have spent time trying to chase down Minna and have narrowed my hypothesis to her being married to Louis See (7 Nov 1882)from the New Ulm, Cat Spring area of Austin county. Looking at death certificates, she had two children with Louis - Adolph (1886-1947)and Bertha (1887-1968). After that Louis is married to a Rosa Hastedt in 1891 and starts another family.
I cannot find any death records for Minna, but I assume she died between 1887 and 1891.
Again, thank you for the help!