A judge in the southern Spanish city of Granada has charged 10 Roman Catholic priests and two Catholic lay workers with child sex abuse.
The 12 are suspected of abusing four teenage boys between 2004 and 2007, the most serious offences occurring in a house used by the priests.
Pope Francis telephoned one of the alleged victims, now 24, in November to offer his apologies.
He acted after the man wrote him a letter about the alleged abuse.
The pontiff, who has pledged zero tolerance of child sex abuse, then ordered a Church investigation.
Several arrests were made in November but the suspects are now free on bail.
According to Spanish broadcaster RTVE (in Spanish), the young man in question and a friend had served as altar boys in the Diocese of Granada.
It is alleged that they were invited by a priest to spend time at his parochial house and at another property, where the most serious assaults were committed.
Following the Pope's call to the alleged victim, the Archbishop of Granada, Francisco Javier Martinez, and fellow priests prostrated themselves in front of the altar of Granada's cathedral to seek pardon for sexual abuse in the Church.
Many survivors of abuse by priests are angry at what they see as the Vatican's failure to punish senior officials who have been accused of covering up scandals.
In July, Pope Francis begged forgiveness from the victims of sexual abuse by priests, and condemned the Church's "complicity" in hiding the "grave crimes" committed by clerics.