what family relative is the narrator supposed to look like?

Nick is sad to look like his Great Uncle.

My family have been prominent, well-to-do people in this Middle Western city for three generations. The Carraways are something of a clan, and we have a tradition that we’re descended from the Dukes of Buccleuch, but the actual founder of my line was my grandfather’s brother, who came here in fifty-one, sent a substitute to the Civil War, and started the wholesale hardware business that my father carries on to-day.

I never saw this great-uncle, but I’m supposed to look like him — with special reference to the rather hard-boiled painting that hangs in father’s office I graduated from New Haven in 1915, just a quarter of a century after my father, and a little later I participated in that delayed Teutonic migration known as the Great War.