I've watched the TV series and am now starting to read the books.
Something that has never been clear to me was the process of kinghood.
There was Robert's way : through force. Then there's the claim of the throne through bloodline. Do they undergo an election system as well in case there is no heir?
I wonder if anyone can explain the possible ways to kinghood and the priorities of all the possible choices.
It comes back to Varys' riddle, posed to Tyrion in Book/Season 2:
Three great men sit in a room: a king, a priest, and a rich man. Between them stands a common sellsword. Each great man bids the sellsword kill the other two. Who lives, who dies?
Varys then gives an answer:
Power resides where men believe it resides. It's a trick. A shadow on the wall. And a very small man can cast a very large shadow.
The qualification for being the ruler is making sufficiently many people believe you are the ruler.
There are many ways of doing this:
We see all of these and more in Game of Thrones. The many characters who rise to become a King (or Queen) typically use more than one of these methods at the same time.
We also see would-be kings who fail because no one believes in them. The most obvious example is Viserys. In theory the law and bloodlines are on his side and he is the rightful King of the Seven Kingdoms; but he has no followers other than his sister and Jorah, because he is unable to inspire belief.
Currently the way of becoming a king in "A game of Thrones" is anything. There is no set rules.
To become a king you have to have the might to shoot down the opposition and fight for it. You have to have the money and power(people to fight and ways to buy them). Just anyone can't do it. You have to have power. Saying that, there might be some other rules, beside "anything goes".
But taking from the title " A Game of Thrones", its a game. Meaning people cheat and people make alliances and people do anything to win. The objective is to win, throughout the books everyone are always coming up with ways to win or trump the others. There is no set rules for becoming a king in this universe.
This question appears to show the rules of getting the kingship's that are the "official rules". Comprehensive Rules for Game of Thrones Lines of Succession
Also, this question appears to show how things are gotten in "A game of thrones". How does one found a house in Westeros?
It is pretty much the same as in real-world feudal societies. There is no constitution or any other fixed set of rules. There is a combination of custom, personal charisma, and the strength of one's army and alliances. For example, Robert was a charismatic leader, and he was supported by several very powerful houses, such as the Starks, the Arryns, and the Tullys. To top it off, he was a distant relation of the Targaryens, which satisfied the custom of a hereditary royal line.
On the other hand, Aegon the Conqueror had no hereditary claim to the throne at all. In fact, there was no single throne of Westeros. But Aegon did have dragons.
Compare that to real-world history, and you will see many similarities. Think of William the Conqueror, the War of the Roses in England, or the history of the relations between England and Scotland.
