This is only for one episode ('The Man with Two Brians' in US season 7/UK season 8), since it's a cartoon and the episodes don't tend to follow a chronological pattern. The family get a new dog, which they name 'New Brian', on account of them feeling that Brian is too old and may die soon due to drinking and smoking.
Brian is fully heard & converses with everyone because that's the way the character was designed. He's simply an anthropomorphic dog.
The purpose of the character Brian on the show Family Guy is two fold. He supplies comic relief while also saying things as a canine that a human would not be able to get away with saying.
Because he just can
Because that's what Seth named him.
Brian
Brian from Family Guy goes crazy for snozages.
Brian the Bachelor
Brian Griffin
A Woody
Brian
Brian from Family Guy goes crazy for snozages.
Brian the Bachelor
Brian Griffin
No.
The character of "New Brian" was featured on the animated television series "Family Guy". The series premiered in January 2009 for the Fox Broadcasting Company.
Brian the Bachelor
A Woody
Brian Does Hollywood
No such character exists on Family Guy
Brian: Portrait of a Dog
Brian has a liberal political philosophy