I cannot prove that the two boys on this postcard photograph are brothers.
The postcard lacks any indication of location, date, or studio.
But the closeness of the figures, the similarity of the nautical-themed outfits, and some shared features suggest to me that they are siblings.
The shorter boy wears a matching blouse and shorts – and sports a jaunty scarf at his neck.
The taller boy is wearing a white blouse and dark knickers – his kerchief is even more flamboyant than that of his brother.
It is pleasing to see that the boys appear happy; one wishes that we had more information about their lives.
One hopes that they grew up with happiness and security in the early 20th century.