My g-grandfather changed his surname as a young man in order to marry a young lady who had four sisters and no brothers to carry on the KERSHAW name. I have found info on him under the Kershaw name. His daughter, named her first son Martine Kershaw; another son, my dad, William Provost; another, John Todd and the last son, Edward Cabbell.
All the middle names were "family" names.

I did find a census report from 1830 with a "James Martine Provost" who was 8 years old; however, nothing more until 1840 and then he was under the new name he assumed...James Martine Kershaw.

If anyone has heard of a James Martine .... changing his name for a young lady, I would be interested. By the way, the young lady married someone else after he changed his name!