Coco is the father of Brian Griffin and mate to Biscuit.
As revealed in "Don't Make Me Over", Coco had a racial problem. His son Brian seems to have inherited this trait from him. Brian frequently barks uncontrollably at black people, blaming his father. This problem was brought up again in "Chick Cancer".
In "Fast Times at Buddy Cianci Jr. High", it was revealed by Chris Griffin that Brian's dad's name was Coco and was hit by a milk truck.
When Stewie gives Brian an award he made for being a "good dog" in "Brian's Play", Brian tears up and wishes his dad was alive to see it.