Peter Gray (Marcus Giamatti) is Amy and Vincent's older brother. He is the eldest son of Maxine Gray. He is an accountant and inherited the family business after his father died. His wife's name is Gillian.
Peter and Gillian struggle to have children and later adopted the son of a pregnant teenage girl named Evie. Their son, Ned is born half Caucasian\half African-American. Some time after Ned is adopted, Gillian becomes pregnant and gives birth to a son named Walt.
After Walt is born, Peter and Gillian's marriage take a rocky turn which causes them to separate and even date other people. Peter goes through a rebellious phase near the end of the series until he discovers his business is almost bankrupt. Later, he and Gillian get back together.