John and Sumner Paine
John and Sumner Paine were members of the Boston Athletic Association, and the first siblings to ever compete together in the modern Olympics.
After the events, Sumner returned to work in Paris while John traveled in Italy with his parents.
NOTE: The website america-scoop.com has a biography of John Bryant Paine. On it, they posted this image of two boys and labeled it “Sumner John Paine” in a section about the two young men competing in the Olympics. While not verified, we have no reason to believe it’s inauthentic, and thought it was too cool of an image to not include here.