John F G Blanchard was born in 1856 in Deptford, London. His mother Sarah Ann Fittock, granddaughter of a coffee and eating house keeper of Deptford, and his father John Blanchard of Winchester Hampshire, a naval dockyard carpenter, married on 30th September 1855 in Deptford. Their six children were born in Deptford.

They named their first child using both their father's names. John Frederick George Blanchard was born on 25 August 1856. A brother who only lived a few weeks followed him and then his four sisters: Alice Mary Ann, Emma Sarah Ann, Keziah Elizabeth, and Ada Abigail.

Although the family grew up in Deptford in the 1881 Census they were living at 11 Duke Street, Portsea Island. John senior was working as a joiner, and Keziah and Emma were employed as stay fanners (i.e. corset makers). The census shows John junior as an able bodied seaman aboard The HMS Duke of Wellington in Portsmouth Harbour.