I know this query from you is years old, but I just googled Uncle Karl(the real uncle and guardian of my first common-law husband, Francois Klanfer, and found your request for info. In case you're still looking: Karl's first wife was Dr. Thompson. (I still have her crimson silk damask drapes hanging in my livingroon.) After she died, he married Tante Herta, a wonderful, kind-hearted Viennese lady who I adored. They lived in Swampscott, Mass., about 20 minutes outside of Boston. Not sure what year they adopted Johnny, but I believe that he was very young at the time. I met him only once when Herta was driving me back to Toronto from a visit to Swampscott,and we arranged a brief meeting at a Howard Johnson's. He was very nice and likeable. This would have been around 1970.
If this sounds like the John Klanfer you are enquiring about and if you would like more info, I can direct you to his brother, Francois, who should know all the details, although they were never close.
lived in Swampscott, about 20 minutes outside of Boston. Francois was the son of Karl's brother and his wife, who was a journalist in Paris.