Pope Francis says he's looking for a "sincere, open and fraternal" debate about divisive family issues that opens Sunday, with progressives hoping for change and conservatives intent on keeping the status quo.

Francis made a cameo appearance Saturday at a twilight prayer vigil in St. Peter's Square on the eve of a two-week meeting of bishops aimed at making the church's teaching on sex, marriage, divorce and homosexuality relevant to today's Catholics.

Francis said he wanted the bishops to listen — really listen to what the people of God are saying — and then engage in a "sincere, open and fraternal" debate that will respond to the "epochal changes" that Catholic families are living through today.