A File:Personal-union-icon.png personal union is a form of diplomatic relationship where one monarch rules over two nations. It can be formed by having a royal marriage with country whose monarch who dies without an heir (usually of the same dynasty). It may also be formed by enforcing a claim through war or, in certain nations, through an event or decision. Once formed, it works similar to vassalage: the nation leading the union (the senior partner) gains the throne and puppeteers the nation who lost their monarch, (the junior partner). As of 1.8, personal unions can only be formed between Christian monarchies.