I saw a Latin inscription in a church in Rome years ago, and there was an interesting feature. It mentioned a pope and his filius. We were a couple of Latinists and we agreed that so it said, but we didn't know why. There seemed to be two options:
- The pope had a biological son.
- The other person might be the pope's protégé of some kind.
For most people the first option is more likely, but we thought that popes are less likely to have a son than most other people. This likeliness may have varied over time, but this is not actually important to my question. I would like to know if the second option would really be a possible reading of the word filius.
Does filius always refer to a son or some other biological descendant, or can it also refer to a protégé of some kind? Is such non-biological use, if it exists, restricted to adoptive sons? For example, can a teacher refer to his student as a filius if there is no family relation between them whatsoever? I am only interested in a filius of a person, not expressions like fortunae filius.
Lewis & Short seems to say that a person's filius is a biological descendant, most typically a son. However, the inscription was certainly not from classical antiquity, so the definition of L&S might not have been valid when it was inscribed.