The problem with this painting is that it is rendered on a black background. Without the ability to see the context of where the children are arranged against the backdrop of their parents and grandparents, the eye is drawn to the fact that they appear to be superimposed against one another, floating in gloom and doom.
In five minutes, someone could photoshop a tiled floor and the barest details of a simply room onto this painting and it would immediately change the way that the eye is drawn to the fact that the subjects are floating in the ether. I think that this is what undercuts the painting. That, and the eye is drawn to the light that illuminates the structures in the background.
My other lame piece of analysis centers around the harshness of depicting people without anything flattering to offset their inherent lack of appeal. This is a royal family? They could be Kardashians. There is no majesty, only the dark severity of the Danish national character.