A surprising number of the Aurelian vampires appear to have been Catholic when they were human. This is odd since most of them are English, which has been a Protestant country since the Reformation.
In canon we do not know exactly how old he was, but he was old enough to have lost his looks by the time he sired Darla, so assuming he was European then it is very unlikely he was anything other than Catholic.
When the Master came to her he was described as a
priest and addressed as
Father (Darla). At that date those were strictly Catholic terms, but then so is the whole notion of a death-bed visit being more important than the doctors work. So the inference is that Darla herself was a Catholic, or else why would the doctor have considered the priest could do anything for her soul?
In late sixteenth century England to be Catholic was not just unusual it was actively illegal. Indeed all the Jamestown settlers were required to take an oath of allegiance to the Church of England before embarking. This means that Darla would have spent her life doubly outside the law, as both a prostitute and a Catholic. The tolerance of the doctor for her ‘heresy’, not to mention quite where he thought a Catholic priest had come from, remain a mystery.
The young Liam was not worried about being discovered at home drunk since he was confident his father would be at confession (The Prodigal). Confession is a Catholic rite, not a Protestant one.
Since Galway is in the predominantly Catholic part of Ireland it is not surprising that Liam’s family were Catholics, although it is worth remembering that at that date their religion would have prevented his father, a merchant, from prospering in business as much as he might otherwise have done. A Catholic could not vote or hold land with any security of tenure, and the most advantageous business contracts would tend to be given to Protestants.
Now by this date it is possible that Drusilla was not a Roman Catholic, but an Anglo-Catholic, that is a member of the Church of England that followed many of the practices of the Roman faith. However, even assuming she was a Roman Catholic, Drusilla would have grown up knowing little discrimination for her families religion and would have had a wide choice of convents to join, since by the mid Nineteenth Century (after the Emancipation Act of 1829) British Roman Catholics were almost free of any religious penalty. The only odd thing about her religion therefore is the appearance of the church: since all the old churches in England were converted to the Church of England rite and the building of Roman Catholic ones was not tolerated until the nineteenth century, all Roman Catholic churches would be relatively new at that date. They also tended to follow an architectural style more akin to continental churches than the native Protestant ones. This therefore makes Anglo-Catholicism slightly more likely than Roman Catholicism in Dru’s case.
It is worth noting that Holtz was a Catholic since his wedding was performed by a Catholic Monseigneur (Offspring). This means his daughter would have been a Catholic as well.
This only leaves:
Who is in fact the only one of the Fanged Four who was not definitely Catholic. Since the majority of people in England in the 1880s were Protestant in one form or another it is most likely he was as well, but there is no definitive proof one way or another.
Described himself as a Puritan (Somnambulist). The term has very little relevance after the seventeenth century, but he obviously wasn’t a Catholic.
So, from a sample of seven, five were Catholic and only one Protestant, with one unknown. About Luke, The Anointed One and other assorted hangers-on we have no knowledge.