The changes were announced July 21 in Washington by Archbishop Carlo Maria Vigano, apostolic nuncio to the United States.
The Pope appointed two priests from Los Angeles and one from Chicago, the rector of Mundelein Seminary, to be auxiliary bishops.
Msgr. Joseph V. Brennan, 61, vicar general and moderator of the curia in Los Angeles since 2013, is a native of Van Nuys, California, whose studies and assignments have all been in the Southern California archdiocese.
Msgr. David G. O'Connell, 61, is a native of County Cork, Ireland, who studied at All Hallows College in Dublin before being ordained a priest of the Los Angeles Archdiocese in 1979. He has been pastor of St. Michael's Parish in Los Angeles since 2003.
Father Robert Barron, 55, is a native of Chicago who has served as rector of Mundelein and president of the University of St. Mary of the Lake, also in Mundelein, Illinois, since 2012. He is founder of Word on Fire Catholic Ministries.
Bishop Wilkerson turned 75 last October. Canon law requires bishops to offer their resignations at that age. A native of Des Moines, Iowa, Bishop Wilkerson was ordained for the Los Angeles Archdiocese in 1965. He was ordained an auxiliary bishop Jan. 21, 1998.
Bishop-designates Brennan, O'Connell and Barron are expected to be ordained bishops this fall, though no date has been set yet. A news conference on their appointment was scheduled July 21 for 1 p.m. (Eastern time) at the Cathedral of Our Lady of the Angels.
Los Angeles is the largest archdiocese in the country by population, with about 4.3 million Catholics.
Headed by Archbishop Jose H. Gomez, the archdiocese currently has four active auxiliaries -- Bishops Edward W. Clark, Thomas J. Curry, Oscar A. Solis and Alexander Salazar -- and with Bishop Wilkerson's retirement, there will be two retired auxiliaries; Auxiliary Bishop Joseph M. Sartoris retired in 2002. Archbishop Gomez's predecessor, Cardinal Roger M. Mahony, retired in 2011.
"It was a complete surprise," Bishop-designate Father Barron said about the appoinment in an interview with The Tidings, newspaper of the Los Angeles Archdiocese.
The author of almost a dozen books and a weekly radio commentator, the priest founded the nonprofit Word on Fire in 2000. The ”Catholicism" television series creator is a regular presence on YouTube and the Web giving a Catholic perspective on mainstream cultural events.
While he is a sought after speaker, he said his main responsibility will be to serve as auxiliary bishop.
"I have to be present to the people of the archdiocese," he said.
The appointment came as a surprise to Bishop-designate Brennan as well.
"It was like a punch in the stomach," he said. "I had an immediate gut reaction that my life was going to be very different. We make our plans, but God has other ideas."
Bishop-designate Brennan, who identifies mostly with his ministry as a pastor, has brought that pastoral sense to his role as vicar general.
"It's a laying down of your life on a daily basis," he said. "I think this episcopacy will be the same."
Bishop-designate Brennan said he, like Pope Francis, makes it a point to bring joy into his ministry.
"I try to bring a real sense of gratitude for the day," he said. "Even in the midst of difficult decisions and the problems and situations that need to be dealt with, without being flippant, I try to be joyful. I try to bring some humor to it."
Bishop-designate O'Connell, who has been serving in parishes in South L.A. for more than 25 years, has ministered to communities that have suffered through gang violence and drugs.
"I do believe what's really important is for us to be out in the neighborhoods, to be out with the people," he said, explaining that his parishes always did Posadas and Stations of the Cross in the neighborhoods, not on church grounds.
"That's how we can change South L.A. is to be out there and work with the people in the neighbourhoods," he said. "I've always loved them. I've always loved being in these parishes."
Bishop-designate O'Connell, who serves on the Archdiocesan Finance Council, works with community leaders and law enforcement on gang intervention efforts.