User blog comment:Fegaxeyl/The Anglo-German Union/@comment-1376885-20110603112612/@comment-257949-20110603114643

According to the creator of the timeline, Wilhelm comes to power because he would be the only successor to the throne after the death of most of the British monarchy. A diarchy would just be unsustainable in the long run. Besides, back then it wasn't unheard of for two territories to be united in this way... just not on this scale.