The Gibb brothers are British. Barry, Robin, and Maurice were born in Douglas, Isle of Man, an island in the Irish Sea, which is not a part of Great Britain, but its inhabitants are British citizens. Andy was born in Manchester, England. Barry, Robin, and Maurice are each recognized as Commanders of the Most Excellent Order of the British Empire (CBE).
So yes, the group originated in Redcliffe, Queensland, but the principal members were British.