The most likely candidates for immediate membership in a commonwealth union would be Australia, Canada, New Zealand and the United Kingdom, commonly known as the CANZUK nations. These four countries share the strongest historical ties, a common language, and a monarch in a kind of personal union which political scientist Peter Boyce has called “an achievement without parallel in the history of international relations or constitutional law.” Further, relations been the CANZUK nations are stronger than between other commonwealth realms and nations as many citizens have relatives in one or more of the other countries.
Given the strong ties between the CANZUK nations, a commonwealth union would likely start with some form of merger of those countries. It could then expand to include the other commonwealth realms, and eventually even some of the other commonwealth nations.
Member states are in blue; suspended member states are in orange; former member states are in red; sovereign states and their territories with historical links to the United Kingdom are in blue.
There is also the possibility of including countries with historical ties to the British Empire, namely the United States, which shares many of the same similarities as the core CANZUK nations save its want of a monarchy.
United Commonwealth 