Definitions of commonwealth
the Commonwealth (of Nations) (formally the British Commonwealth) is an organisation of about 50 countries that were once part of the British empire (=a group of countries consisting of Great Britain and its possessions, dominions, and dependencies)
Rwanda was admitted to the Commonwealth in 2009.
a group of countries with political or economic connections
The 89-year-old said he would not seek compensation from the commonwealth because he wants to spend his final years in peace.