I suppose it doesn't help with your family being 'diet saboteurs'...shame on them!
Like you my weight crept up over the years and I would lose it then put it back on again. Two years ago after completing the DAFNE course I decided to make a determined effort to shift the weight once and for all, I sort the advice of my dietitian at my local hospital and together we looked at the calories I was consuming and ways in which I could cut back, at this time I also bought an exercise bike and increased the duration of my dog walks both morning and night, altogether I was exercising around 90 minutes a day (more on a weekend).
I didn't lose weight quick and it took me nearly 2 years to lose the weight I needed to shift ( 29lbs in total) but the way I look at it the slower you lose the weight the less likely you are at putting it back on, so far I've kept the weight off although it does fluctuate 1-2lbs.
Therefore it might be worth you talking with your diabetes team and ask for assistance from the dietitian to look at your diet, joining a gym or local activity group would also help as would joining a slimming club such as Weight Watchers or Slimming World, my wife (non diabetic) lost 3 stone with Slimming World and I believe they do now cater for people with diabetes, some type 2's on the forum have lost weight successfully with both clubs although I've not seen anyone posting who is a type 1......but you can certainly enquire just the same.