While I don’t believe that animosity between cousins played a major role in the descent to war in 1914, animosity between Wilhelm II and his Russian and British cousins certainly did exist. As you are aware, Nicholas II, Wilhelm II and George V were grandchildren of Queen Victoria. As a child, Wilhelm holidayed in Great Britain and whilst he enjoyed his grandmother’s acceptance, he was largely ostracised by his cousins who viewed him as arrogant. Historians have poured over Wilhelm’s personality and have suggested that Wilhelm possessed an inferiority complex in regards to his relationship with the British. Forgive my use of a quote from Wilhelm’s Wikipedia page but I don’t have my copy readily available. David Fromkin has written that: “From the outset, the half-German side of him was at war with the half-English side. He was wildly jealous of the British, wanting to be British, wanting to be better at being British than the British were, while at the same time hating them and resenting them because he never could be fully accepted by them.”

I believe that Wilhelm’s desire to be “better at being British” led him to pursue foreign policies intended to establish Germany as a colonial empire in competition with the British. This inevitably brought Germany into diplomatic conflict with Great Britain. Wilhelm’s most ambitious action and probably most damaging in regards to Germany’s relationship with Great Britain was his decision to pursue the construction of a naval fleet intended to directly challenge Britain’s control of the world’s oceans. This of course established Germany as a threat to Britain’s colonial empire, a factor that does play a role in the descent to war in 1914.