Some questions apply to language families, but I doubt that it's the majority. Language families are mostly grouped by vocabulary, they can have rather different grammar, spelling, phonology, etc.
A tag like romance-languages on a question about, say, how to train oneself to pronounce the letter
R, or when in a curriculum to teach the subjunctive, would be meaningless. Such a question should be tagged french or spanish or italian etc. as appropriate: these questions have completely different answers in different Romance languages.
There are questions that apply to a set of languages, not necessarily grouped by historical families. Such questions should be tagged according to what makes the question distinctive. For example, a question asking specifically about leveraging similarities between Romance languages should be tagged romance-languages. A question asking about teaching language features such as tones, cases, etc. should have a tag corresponding to that language feature.