That close inter-marriage has genetic side-effects, too.
My gf & I often comment that visiting Europe in the Edwardian era and maybe between the wars would have been very interesting from an arts & culture point of view... as log as you could "get out of Dodge" on a moment's notice.
I've been reading up a bit on Kaiser Bill. Apparently very intelligent and made many valuable reforms in education and various social issues; promoted interest and research in promoting science and the arts. But also deeply insecure and jealous of Britain's position as top dog, which fuelled his nationalism. Also frustrated by his physical disability, which curtailed his participation in military activities, with which he became almost obsessed.
I remember reading an anecdote of a visit to Switzerland, where he observed some very accurate shooting by the small Swiss army (~100,000) He expressed his admiration, but added, "But what would happen if I were to invade with an army of 1 million?" To which the commanding officer said, "Well, we'd each shoot 10 times and then go home."