Wilhelm was born the son of German officer of the Prussian Army Ernst Curt Sigismond Diederich and his American wife Eleanor "Ellen", née Hunt.
[2] After his marriage to a German countess, Diederich and his family lived in Bavaria until 1941 when they returned to the US due to World War II.
Diederich first married "Maria"/"Mary" von Anders on 31 August 1912 with whom he had two children.
Wanda Diederich died tragically in late fall 1951 when the family home in Tappan burned down.
Burgthann Castle, bought by Wilhelm in the 1920s, was inherited by his daughter Diana (1930–2004), who sold her ownership of the castle to the municipality of Burgthann near Nuremberg (Bavaria) in 1988[4] Son Harold Michael (born 7 February 1933 in New York) was killed in action on 24 June 1952 as a Marine during the Korean War.