William was the son of Harrison Gray Otis [1856-1915] and a descendant of Harrison Gray [1711-1794]. Harrison Gray was the receiver-general for the Province of Massachusetts from 1753 until the Revolution, and the sitter for a portrait by John Singleton Coply now in the NGA (1976.25.1). Harrison Gray's daughter, Elizabeth Gray Otis, married Samuel Alleyne Otis [1740-1814], brother of pamphleteer James Otis and author Mercy Otis Warren. Both Samuel Alleyne Otis and Elizabeth Gray Otis, are subjects of portraits now in the NGA (1980.11.1, 1980.11.2). [Compiled from sources and references recorded on CMS]
Bibliography
1924
Otis, William A. A Genealogical and Historical Memoir of the Otis Family in America. Chicago, 1924: 608.