W.T. and Sir John A.
Canada was founded in 1867 with Sir John A. MacDonald (a notorious drunkard) as the first prime minister. The Irish Free State was founded in 1922, with W.T. Cosgrave as the first President of the Executive Council. Both countries were dominions of the British Empire. In 1937 Ireland became a republic. Canada never did, and has a queen. (Both images taken from the respective Wikipedia biographies.)
W.T. Cosgrave (1880 - 1965)
Sir John A. MacDonald (1815 - 1891)