An explanation of Brandon

Lots of people seem to be confused by Brandon's actions. It's because Nightow likes to create INFJ characters, and they are in nature extremely complex.
It's a rare personality type. He's a really good personification of it too, in fact. Despite being seemingly different characters, Brandon and Vash act on the same mindset.

Miyazaki tends to do this a lot too, with characters such as Haku, Ashitaka and Howl.

http://www.typelogic.com/infj.html
http://en.wikipedia.org/wiki/INFJ
http://www.mypersonality.info/personality-types/infj/