“Uncle Christian and Gaerttner family?” Thank you to Martim Koepple of Plochingen for help on this. I don’t recognize the name Gaerttner, but I can see the name Karl Gaerttner on the plaque over the door in the lower photo. It is only visible on the higher resolution digital photo, not posted here.

I would guess that Christian Maier has a daugther married to the younger man in the photo whose surname would be Gaerttner.