There are two forms of diabetes: one is the failure of the pancreas to produce insulin or the body's inability to use the insulin to control blood sugar, which is often known as Type 1 or Juvenile Diabetes.
And then there is Type 2 diabetes where the insulin production is not enough to control blood sugar levels. Diabetes is also a disease of old age. The pancreas is one of the first organs to give out.
In my case, NO ONE in my family had it but me. Not my parents or grandparents, their siblings. And not my kids. Sometimes it's just bad luck. And some think it might be caused by a virus and I might have been exposed to the virus.
I became diabetic when I was a reporter in Syracuse. Curiously, there were a lot of employees at the station with diabetes, and for a small TV station it was very unusual. I once mentioned this years later and it was suggested that I report this to the CDC for investigation but I never did.