Well depend if you consider Alexander I wife Victoria being the first
and anyway our dear queen wil always Number one in my hearth
((OOC: Its similar to Decades of Darkness, Kingdom of Canada, if you need a basis, its more or less official but Queen Victoria didn't exist in that timeline or was born a guy, but anyway the most important is that Basicly Canada doesn't have the same ruler as the United Kingdom))
William I, because of his charisma, remember how he rallied the people of Canada during the great Quebecois war, and lest we forget his role in the formation of the Californian Republic.
Alexander I because he was canny political bastard. He survived the scarlet revolution in the UK with enough prestige to guarantee him standing in the former colony. He triumphed against his rival claimants and was coronated with popular appeal. He succeeded in keeping the always unruly 13 provinces within the kingdom by pitting the various regions against one another. Most importantly he kept Louisiana at bay and Canada's borders largely intact.