Hey Watson, i'll try to help you the best I can from what I understood of your story. As a religious person myself (protestant), I can tell you that it is perfectly fine about being curious about -- and questioning the things you don't understand to people who know better than you (the priest in this case). I don't really know what this "ethical question" was, but I don't think it really matters as I would say that it is always better to ask questions about religious elements which don't make sense to you, so you could get guidance and advice on this matter.
However, it could actually depend on what you asked the priest, as catholic churches tend to be much more stricter about behavioural conduct and such. Nonetheless, it seems that the priest himself was happy to speak to you about the matters, so I would disagree on the part where you compared this scene to that of you calling up your mom's boss and asking personal questions. From what i've gathered, I don't think that you are in the wrong, and I think that the family member of yours is in the wrong here for not trying to help you understand the religion further, but instead is telling you off for thinking you potentially risked his/her job (which shouldn't be his/her priority imo). It would help though if you could tell us what the ethical question was, but this is the best I can do to help you understand the situation from the information I was given.