I did find Daniel F. Greenwood's obit, from Phoenix, AZ..It did not mention his brother William..Also, another brother John F. Greenwood died in Yavapai Co, AZ on 3/26/1932..Here is his death certificate (link)..Parents listed as Daniel F. Greenwood & Winnifred Warren..

http://genealogy.az.gov/azdeath/045/10452499.pdf
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Gay