Yes, your chances will be very high, but it is not certain. It also matters what type of diabetes they have. If they have type 1 Diabetes, and you are over the age of 30, then it is pretty unlikely that you will develop type 1 diabetes; but its still possible to develop type 2. Knowing this it is pretty important for you to be taking care of yourself physically; this meaning you should be on strict diet, and exercising at least 30 minutes a day.
Your chances will be very high.