The relationship between Ireland and Britain

Let me tell you something. I have been studying in England for four years, and I am more or less sure.

Ireland and Britain are both members of the European Union, which is a state-to-state relationship.

Ireland was a part of Britain in its early years and later became a member of the Commonwealth. 49 years later, Britain recognized Ireland's independence.

However, due to historical reasons, Irish citizens can move freely between Britain and Ireland and enjoy British citizenship in Britain.