Catholics wishing to get married in St Peter’s Basilica, specifically in the Choir Chapel, should contact the priest who is available to celebrate the marriage. They should send an official request to the Prefecture of the Papal Household, justifying the importance of getting married in St Peter’s Basilica, as well as a letter of suitability signed by their parish priest attesting that the bride and groom are faithful and active in the life of the parish.
To celebrate baptisms in St Peter’s Basilica, you should also check with the priest who is available to celebrate the wedding.