How is a cadet house born ? Maekar has his own castle ( summerhall) and his son inherits it but he is still a targ. Karlon stark has his own castle but he changes his surname . Thank you

Well, Maekar isn’t a great example because he was the heir of the main branch and then inherited. Also, it’s never been clear whether Prince of Summerhall is a title that one retains for life – I.E, if Aerys I had two sons and the oldest is the Prince of Dragonstone as per tradition, does Maekar cease to be the Prince of Summerhall and the youngest son of Aerys takes the title?

Moreover, the surname doesn’t make a cadet branch either – the Lannisters or Lannisport are a cadet branch, and look at all the Flints all over the North, and so on and so forth. What makes a cadet branch is a separate fiefdom and line of inheritance that persists over time, so that they’re broadly seen as a separate family. 

Could the Bracken-Blackwood feud be solved by creating a buffer house in between them. Say a second son from one of their houses and a daughter from the other is given Pennytree, and the houses give the disputed lands as a dowry/bride price to this new house.

Given how many Bracken-Blackwood marriages have failed to do this, I don’t think it would work: chances are, they’d gang up on the buffer house and then turn on each other once it’s destroyed.

“I, against my brothers. I and my brothers against my cousins. I and my brothers and my cousins against the world.”

If Ulmer is to be believed, they just robbed her. 

So they robbed her when she was en route to her wedding to Rhaegar?

Do you think that’s when the Crown decided things had really gotten out ofhand, and sent Selmy and Dayne to deal with the Kingswood Brotherhood?  

Text doesn’t say, but I would guess it would have been a major embarassment for the Crown so it probably moved the issue up the chain. 

Were there real historical examples of “mystery knights” competing in tourneys? If so, why would they want to compete anonymously? It doesn’t make a lot of sense to me even in ASOIAF.

Jousting in disguise was a big thing in chivalric romance, and thus trickled into the real jousting culture. Henry VIII, for example, loved to joust in disguise. 

As to why, well it boosts the drama and attention: people want to know who the mystery knight is, so there’s all this tension that gets built up and then released when you have the unveiling. 

Maester Steven, may I please ask if you have read any of Mr Robert Harris’ CICERO Trilogy? (one must admit to having enjoyed it so much that my Alternate History username is drawn from the series, but I would be interested in learning if you have read these books and would be still more interested in hearing your thoughts on them should this be the case).

Yeah, I read a bunch of them. They were pretty good, if heavily Ciceronian in their political leanings, although you’d expect that.