I come at this from the opposite direction not being diabetic. When James got his diagnosis, four years ago, it was me who found out about low carb, cleared the cupboards and said what would or wouldn't be eaten in this house from now on. I have mentioned elsewhere that this was not the easiest few days of our marriage, but as sky high (I think he was at 24mmol/L on diagnosis) blood sugars dropped to normal within days, clearly I was right, as usual!
Along with James, I have been low carb/ketogenic for the full four years, barring the odd relapse if we are dining out, which doesn't happen that often. James has never broken ranks.
I am slimmer, healthier and happier than I was four years ago, so the point I am trying to make is, don't think that you can't expect your family to join you on your restrictive diet, see it as an opportunity for them to eat better, perhaps avoid future diabetes and other illnesses and to improve life for your whole family. Of course they can have a beer/bagel/chip butty or whatever floats their boat from time to time, but move towards these things being the exception rather than the rule.
Sally