The following information was submitted by Roger Davis, a collector and researcher of Foster's work, in May of 2006:
This comes from the Gloucester vital records (vr), as well as census records available on ancestry.com.
"John B. Foster was born in Gloucester on Christmas Day in 1865 (vr), the son of John B. Foster, a fisherman who emigrated from England, and Sarah E. Merchant (or Marchant), daughter of an established Cape Ann fishing family. His father was apparently lost at sea when he was young and his mother remarried. By 1888 he is a professional artist, listed in the Gloucester city directory. By 1897 he is living in Boston where he marries Emma Allen, born in England (vr). They have at least two children, Edith and Marion (vr). The family moves to Somerville (census 1910,1920) and then Pepperell MA (census 1930). In each census John lists his occupation as artist."