Brendan John Cahill, 51, was born in Coral Gables, Florida. His family moved to Houston in 1971. The son of Joe and Joan Cahill, Bishop-elect Cahill has two brothers and twosisters, seven nieces and nephews and a great-nephew and great niece – all of whom live in the Houston area. Bishop-elect Cahill attended St. Cecilia Catholic School in Houston and graduated from St. Thomas High School in Houston in 1981. He attended Rice University for a year before entering St. Mary's Seminary in Houston in 1982.
Bishop-elect Cahill was ordained a priest for the Diocese of Galveston-Houston in 1990. He was as parochial vicar at St. Frances Cabrini in Houston and Christ the Good Shepherd in Spring before serving as the formation director at St. Mary's Seminary from 1998-2001. He later served as the rector at St. Mary's Seminary from 2001 to 2010 and was an adjunct professor at the University of St. Thomas School of Theology. Since September of 2014, he has served as Administrator pro-tem of St. Joseph Church in Houston.