Franz Joseph was the fifth and youngest child of Duke Karl Theodor in Bavaria and his wife Infanta Maria José of Portugal.

[1] Duke Franz Josef in Bavaria visited the US in 1910 and hunted grizzly bears though the US press speculated on a possible American match (so popular at the time).

The speculation was furthered when Franz Joseph commented on his cousin Prince Miguel's lovely American bride, Anita Stewart.

Duke Franz Josef also spent time in New York City, where he stayed at the Plaza, and he was the "most-talked-about nobleman" to visit the US since Prince Henry of Prussia.

Though remaining unmarried, through his relationship with Caroline "Lilly" Stockhammer, he became the progenitor of the von Plottnitz-Stockhammer family, which has produced descendants prominent in politics, education, and the arts.