VATICAN CITY (CNS) -- Pope Francis formally approved the delegates to October's synod on the family elected by 28 bishops' conferences, including the U.S. Conference of Catholic Bishops; other conferences have yet to elect their delegates or have done so only recently.

The pope approved the U.S. bishops' election of: Archbishop Joseph E. Kurtz of Louisville, Kentucky, conference president; Archbishop Charles J. Chaput of Philadelphia, host of the World Meeting of Families in September; Cardinal Daniel N. DiNardo of Galveston-Houston; and Archbishop Jose H. Gomez of Los Angeles.

The U.S. bishops' alternates also were approved. They are Archbishop Blase J. Cupich of Chicago and Archbishop Salvatore J. Cordileone of San Francisco.

The Vatican announced Jan. 31 the names of the delegates approved by the pope. The world Synod of Bishops will be held Oct. 4-25 at the Vatican and will focus with the theme, "The Vocation and Mission of the Family in the Church and Contemporary World."

It follows the extraordinary synod on the family in October 2014, which Pope Francis said was designed to present an overview of the situation of families and the primary concerns for the church's pastoral care of families.

For the 2015 gathering, the bishops of England and Wales elected Cardinal Vincent Nichols of Westminster and Bishop Peter Doyle of Northampton.

The Irish bishops elected Archbishop Diarmuid Martin of Dublin and Archbishop Eamon Martin of Armagh, Northern Ireland, president of the Irish bishops' conference.

The bishops of Australia elected as their representatives Bishop Daniel E. Hurley of Darwin and Archbishop Mark Coleridge of Brisbane. The bishops of New Zealand chose Bishop Charles Drennan of Palmerston North.

The number of delegates each bishops' conference elects to a world Synod of Bishops depends on the size of the conference. Those with fewer than 25 members elect one delegate; those with 26-50 members elect two; those with 51-100 elect three; and those with more than 100 members elect four.

In addition, the Union of Superiors General of men's religious orders elects 10 members.

The heads of the offices of the Roman Curia are automatically members, as are the heads of the Eastern Catholic churches, which elect additional delegates according to the size of their church synods.

Pope Francis also will appoint members; papal appointees usually are chosen to improve the geographical mix of the synod's voting members and to include bishops with a special expertise in the topic under discussion.