He and his three brothers, John, Edward, and Michael, are joined by their only sister, Christine Collins, as the five children of the late John and Gloria (Marchetti) O'Brien.

The oldest of the five, he was born in Everett on March 6, 1960. He attended Everett Public Schools, including Parlin Junior High, before traveling next door to attend Malden Catholic High School, Malden.

A long-serving member of the Everett Fire Department, he was granted a bachelor of science degree in fire service administration in 2010.

He and his wife, Karen (Willis) O'Brien, are the parents of five: Anthony of Saugus; Matthew of Windham, Maine; Meghan Pouhle of South Portland, Maine; and Colleen and Catherine, both of Brooklyn, N.Y. His son Anthony and his wife Courtney are the parents of his four-month-old granddaughter, Louisa.

He and his wife are parishioners at St. Theresa of Lisieux Parish, North Reading, and during his deacon formation, he served at a chaplaincy internship at Tewksbury Hospital.