kaiser

de.wikipedia.org/wiki/Kaiser-Wilhelm-Denkmal_(Essen) Using Google Translate "After the foundation stone was laid on August 26, 1898 without a special celebration, the entire monument was inaugurated on October 23, 1898 in the middle of Burgplatz." "In the course of a comprehensive redesign of the inner city, an urban planning concept was sought in a first architecture competition in 1924 to redesign the Burgplatz in a big city. As a result, the area of the square, which had previously sloped to the east, was straightened and connected to Burgstrasse with a wide staircase. In 1928 the equestrian statue was finally moved to its current location on the southwestern edge of Burgplatz, near the Lichtburg building, directly on Burgstrasse, with a new, simplified base without a terrace." 2017 360° picture of statue in current location at goo.gl/maps/1RstDLe81X7KGhrHA

the youngest Prince also renounced all claim to the throne so he could marry below his station, which the former Kaiser forbade.

Copied by the Bain Agency from a German souvenir postcard. This appears to be a composite portrait of the three, each of whom was photographed separately. That would account for the shadow being on the right half of the Kaiser's face, while on the left half of his son's. And the kid is out of proportion to both of his elders.

Another Bain Agency photo shows the sons without the Kaiser:

Wystan: Thanks for sharing the related photo. We will add more information to the description when we update.

The man in the dark uniform is Prince Adalbert of Prussia (1884–1948).

The second man from the left might be Prince Joachim of Prussia due to his "Deaths head" hat insignia.