The earliest Fonblanques we have found used the prefix ‘de’.
The English branch of Fonblanque
When Abel de Grenier de Fonblanque sent his sons Jean and Antoine to England in 1740 they became anglicised as John and Anthony Fonblanque. They both became English citizens at different times John in 1748 and Anthony in 1758.
De Fonblanque in England
John Anthony Fonblanque petitioned George III to resume the name of de Grenier de Fonblanque in 1825 and this was granted although not all of his descendants chose to use the name.