Err no Canada and Australia are not part of the UK and never have been - They were part of the British Empire but gained there own independence many years ago - Canada 1867 and Australia 1901, And the USA in 1777.
Great Britain has existed since 1707 and consists of England, Scotland and Wales. They added Ireland(Northern Ireland only after Irish independence) in 1800 and it became the United Kingdom.
Interestingly the only nation of the UK without a sovereign parliament is England ! (Westminster represents all 4)