I am actually pre diabetic and have adopted a low carb diet to try to stave off diabetes. I don't think a one-time high reading is necessarily bad. If you are concerned, have the test again, after fasting for 12 hours. And you can request a test called the A1C which measures average blood glucose over a 3 month period. That might give you more info than a single fasting test.
I don't think eating candies should alter your blood sugar 7 hours later. But I would say to repeat the test as it should be with the fast.
If, and I do mean IF, you are pre diabetic, you should thank your lucky stars to have caught it early. Most people do not find out until they are full blown diabetic. I am 50 years old and on the thin side, and so I didn't think I would get diabetes (but I do have a family history for sure). Like you, I was shocked to see I wasn't immune to it and it was a possibility. If you find out early, you can control this with lifestyle changes. I am not on any meds at all.
Sugar and candy aren't good for ANYONE. Even if you turn out to be perfectly normal, cutting out sugar and starches from your diet will help you in the long run. Your brother also has some reason to be concerned, as a non-diabetic's number should drop farther than that after 4 and a half hours.