I think this is one of those spirit photographs, in which a ghost is captured on film trying to interact with the living. Notice how the bad twin is making a fuss, yet neither Mom, Dad, nor the good twin take any notice. Logically, the bad twin must have wandered off and drowned in the lake, and now his ghost is trying unsuccessfully to attract their attention.
The ghost notwithstanding, it is a terrific photo, and it was Anne, a keen photographer in her own right, who was kind enough to send it to me all the way from the Netherlands. The photographer for this card is unknown, but the image itself is owned by HEMA.