In French history, King Francis II was notable for marrying Mary, Queen of Scots, but he died shortly into his reign and marriage, with no son or daughter either. It's quite remarkable that the show writers fictionalized his life and were quite good at it. The show starts with Franics meeting Mary for the first time since they were children. Both are somewhat happy to be engaged to each other.
I liked his relationship with his half-brother Bash who is the bastard son of his father King Henry II. They are quite loyal to each other, the only thing that tore them apart was a desire for Mary. Though they eventually repair their bond.
In the show Francis often rebelled against his father over issues especially those concerning Mary and Scotland. He led the force to take Calais (England's last hold of land in France since the Plantagenets) and did so quite well. He decides to take his father down before he got too insane and used that power for a force of real evil, not just political evil.
Francis' reign isn't an easy one. He has to deal with plague and trying to care for his bastard son at the same time.
And he is challenged and controlled by Lord Narcisse for most of the start. When Narcisse finds out Francis' secret about murdering his father in the joust, he turns it to his advantage. But eventually Fraincis turns the tables on his "vassal"
Francis and Mary's marriage went through ups and downs. It was tested the most during the second season when Louis, Prince of Conde made the marriage estranged and took Mary as his for a brief time. But eventually they renew their love for one another.
While awkward for all of them, Francis tried to convince Charles to marry Mary after he passed away as he knew he was dying. This would have cemented Mary's power in France, but like history itself, it wasn't meant to be.
I really thought his "death" from the ear disease thing was the final bit, but then he is magically cured.
So he could be killed by rebellious Scots who sneaked into France. Kinda cruel to the show fans who didn't know the real history and thought Francis was actually going to survive the events of the show. I could tell the show makers and cast must of loved the actor Toby Regbo because he stayed far longer than he should have if you look at history. They must of had a hard time letting him go.