Sorry to hear about your predicament, I'm in the same boat. What I did was take control of the fridge and pantry. I write a list and do the shopping, but if I can't, I make my boyfriend do it but to the list. If he deviates from it, he gets an earful. He's allowed his treat but I don't want to see it. The behavioural training has worked well because he only buys yoghurt instead of biscuits and chocolate now. You could also buy low sugar protein shake, and psyllium husks, mix them, and sip them instead of the bad stuff, which works for me.
I also find that filling myself with a massive surge of positive emotion helps. Here is what I would do, call me crazy but it works for me: I see the offensive item, pick it up, imagine myself at the fattest I've ever been, put it down, walk away: and this hurts at first, because I want it soooooo badly and I've had a terrible day and all I wanted was to feel good and relax with an easy meal, but I push that back, deep down and fill myself with a sense of strength and superiority, as though I have just overcomed something monumental, as though I have achieved the impossible. Yes. I replace junk food with smugness
Or in your case, couldn't you just ask your family to replace their fatty meats with Kangaroo, their chips with baked potato and...well...just take healthier options? You would probably all be better off for it. But if not, the tips given by the others above were also very good.