A former friar of the Franciscans of the Atonement, the Archbishop held several degrees including an A.B. in philosophy from St. Pius X Seminary, an M.A. in Theology from St. John's University and an M.A. in Education from Manhattan College. The Archbishop also held several honorary degrees, including the Doctor Divinitatis degree, honoris causa, from the Collegium Augustinianum Graduate School of Philosophy and Theology, the university and seminary affiliated with the Old Catholic Confederation.
An accomplished educator, and former English Department Chairman, Archbishop Brennan served in the New York City High School system for thirty-five years as a teacher and administrator. In his professional capacity as an educator, he was also certified by the New York School System as a District School Superintendent, as an Assistant Principal at the Junior High School and High School level and as a Principal at the Elementary, Middle and High School levels.
Married to his late wife, Mrs. Marie Kirby, for forty years, Archbishop Brennan and his wife had three adult children and six grandchildren. Until his falling asleep in the Lord on August 1, 2016, Archbishop Peter (as he was known) resided with his beloved champion Irish setters in West Hempstead section of Long Island, New York. May he rest in peace and his memory be eternal!