One of William Downs' siblings is Susan Downs Melvin (1850 - 1938). She married John Melvin (1836 - 1913), a blacksmith from Hazlettville, and they are both buried in the Odd Fellows Cemetery in Camden, DE. This is the same cemetery in which John M Downs and his second wife Amanda Melvin are buried. John Melvin and Amanda Melvin appear to be siblings, children of Joshua Melvin and Letitia Jones.

I do not have any obituaries except for a brief one for John M Downs from a Maryland newspaper. It gives his birthdate as Feb 1 1824. This differs from the birthdate on his death certificate, which is Jan 21 1824. The 1900 census has his birth month as Feb, so maybe the newspaper article is correct.