I'm diabetic and it really isn't that big a deal
It just takes a bit of management regarding what foods to eat and remembering to take meds etc.
I wasn't happy when I first found out as I thought my life as I knew it would surely be ruined! But after a few months' adjustment I felt so much better that I ended up being quite glad it had been picked up when it was.
I had put on a lot of weight before diagnosis, in the 2 years since then i have lost 56lbs and have a lot more energy.
If your bro is diabetic, managing his diet and keeping his blood sugars as close to normal as possible will stave off possible complications. Losing limbs and going blind etc are down to bad management of the condition, in the old days when people didn't have the means to test their blood, complications were almost inevitable but that doesn't have to be the case now.