Sara,
I wonder if that man is Robert Wadlow.
I think he was the tallest man ever, and lived in a time period that would work for that car, and the way they are dressed.
He was a bit of a celebrity in his day, which would have made this a key moment to photograph.
https://en.m.wikipedia.org/wiki/Robert_Wadlow
If it is indeed him, the Guiness people may be able verify it. In comparison to the other guy, unless he is an inordinarely SHORT man, the tall man is definitely WAY into 7+ feet tall.
Very cool family heirloom!
- NDG