Hi Cecile, I found a Carl Wunder who was living with his parents in San Francisco, San Fran Co. in 1920 Carl Wunder, b. IL, 17, driver dairy.
I searched Ancestry and FamilySearch but didn't find Carl or Emma in either.
I did find a Robert Fred Wunder Born=24 Sept. 1926, San Francisco Co. Mother's Maiden Name=Koller. Source=California Birth Index 1905-95.
A Robert F. Wunder Born=1926, California Residence=Marin Co., CA Enlisted=13 Nov 1945, Camp Beale Marysville, California Grade=Private Term of Enlistment=Panama Canal Dept., Regular Army Education=1 year high school Occupation=cook Marital Status=single without dependents. Source=U.S. World War II Army Enlistment Records 1938-46.
You will find an obituary volunteer at raogk.org Read guidelines Choose California Choose M thru R Scroll down to Marin Co. and choose ONE obituary volunteer.
OR Contact the Marin County Genealogical Society, maringensoc.org/ . Hopefully there will be something in Robert's obituary about his parents. Successful Searching!