Peter and Brian's Relationship

An idiot man and his sarcastic dog

Peter: I feel there's nothing like the relationship between a man and his dog.
Brian: Except in this case, the man is an idiot and the dog is the only sane member of his family.

— "Peter's in Charge"

Peter and Brian's Relationship was the friendship between Peter Griffin and Brian Griffin.

Details

After Peter took Brian off the streets and make him part of the family in "Brian Griffin", the two have been (mostly) inseparable. The two are like a hero and his sidekick. With Brian playing the brains between the two, using logic whenever they face a problem, and tries to help Peter with his crazy shenanigans or at the very least tries to point out the fallacies in whatever plan of the week he has and tries to point him in the right direction. And Peter plays more of the role of emotional support. Since from very early on, Brian has always been questioning his purpose in life. Not only that but he helps Brian leave his comfort zone and he's not afraid to call him out if he's being a dick. In fact, early press releases markets them as the dynamic duo of the show.

Despite their friendship, it has taken a back seat as the show went on, around the show's fifth and sixth seasons, due to 1, Brian and Stewie's Relationship taking off and becoming the popular duo of the show, and 2, Peter being mad at Brian for trying to fuck his wife in "Play it Again, Brian". And understandably calling off their relationship.