Small victories friend. Don't try anything extreme. Make small consistent changes if you can.
Your family shouldn't have to change because you can't control yourself. If you treat them like an obstacle they won't support you and they'll make it even harder for you to succeed by stressing you out. Instead try to learn how to be a good example, start by showing no interest in all that junk food.
Personally I'm all about diet and exercise but I don't think that means I shouldn't have sweets.
Junk food has its place on the food pyramid.
Small consistent changes. Nothing happens over night.
You have to understand your cravings! Before you start changing your eating habits, go over them and try to figure out what you crave and when. Some people crave sweets while others crave salty food. Some people have food cravings that are connected to physical hunger, while other people might crave comfort foods when they're stressed out or depressed. Keep a food diary if you're not sure when cravings hit.
It's hard to resist a food craving when you're hungry. Eat several small meals throughout the day and never spend more than four hours without some food.
Drink lots of water to avoid dehydration. Your body can confuse thirst with hunger. If you have a hard time drinking eight glasses a day, try herbal teas, diet soda, fresh vegetable juices and sugar-free sports drinks.
Keep only healthy snacks at home. Chances are you will crave cookies, not apples. When you look inside the cupboards and find no cookies, however, you're likely to just eat an apple. This will help you keep full and might help the craving disappear. Stock up on nuts, whole wheat crackers, roasted soybeans, dried fruit and low-fat mozzarella sticks.
Reduce your sugar intake. Sugar affects your blood glucose, triggering quick ups and downs and causing you to crave more sugar. Soda contains high amounts of sugar, and so do fruit juices, some cereals and even cereal or energy bars. Compare labels when shopping and choose the item that is lower in sugar.
As for the rest of the family that likes junk all I can say is tell them if they bring it into the home you are going to put it in the garbage. So tell them they can have it but not in your home!