What is the probability of having diabetes if nobody in your immediate family is known to have it?

Type I or Type II? If you're talking about type ii diabetes, then this depends as much on your own lifestyle risks as on family history. Type ii diabetes is caused by having too much fat around your middle. These fat cells can cause your other cells to not respond to Insulin the way they should, causing the symptoms of diabetes. If you feel you are at risk for this, you should see your doctor and come up with a plan.
Risk factors. The odd then is just like everyone else and depends on your current risk factors: hypertension, low hdl, high cholesterol or triglycerides, history of gestational dm or gave birth to a baby > 9 lbs, or belong to high risk ethnic groups ( african-american, native american, latinos, asian american/pacific islanders).