Sorry, but no. Serbia ist listed to be a member in 1 November 2000, and Montenegro in 28 June 2006.
And Tuvalu is in the Wiki list "List_of_countries_and_dependencies_by_population" behind Nauru. But it is true that there are differences depending on the source
Also Nauru has the 2nd least population i think
And Tuvalu is in the Wiki list "List_of_countries_and_dependencies_by_population" behind Nauru. But it is true that there are differences depending on the source