Since my partner is as obsessed with flying his aeroplane as I am mine, I cannot but add that I think it is about testing the water in the same way one does with other family members: a short flight in smooth air to start with, if at all possible. You can tell fairly soon if there's any interest beyond the sightseeing aspect, or getting from A to B, if that's part of the mission. More importantly, unless you are incredibly thick-skinned, it's fairly easy to judge what your partner/mother/sister/brother is doing. Beyond the polite response, at worst, (if you hate it, say so, you're allowed, you're family...), there are fewer subtle reactions than one might think.
So, having got the response and reactions & read the body language if necessary, you know whether to work on future flights or leave it there for the time being. At least at this stage they can see what a small aeroplane looks and feels like (how many people never get up close to anything with one engine (or none)?) and thus understand a whole lot more about what you are going to be enthusing. For all those who ask the questions and have enthusiasms of their own, there are as many who see what it is and how you love it, but are happy for you to do your thing and will likely be proud of you for doing it too, but just don't want to be involved. Different passions are a good thing too. Just be prepared to do that one round of golf or whatever in the interests of balance
