What sort of ethnic and religious background is your character from?
Bram is a short form of
Abram or
Abraham, and there certainly were boys named
Abram and
Abraham in the late 1700s. For example,
Abram Trigg, born in 1750, was a member of the US House of Representatives:
http://politicalgraveyard.com/families/2100.html
It therefore wouldn't be at all a stretch to call a character from a Protestant English speaking background in the late 1700s
Bram, if it was seen as a pet form for
Abram or
Abraham.
I found some online references to
Ewan as a given name in that time period, but only from the Isle of Man.