Question: Can I get diabetes even if no one in the family has it?
Answer: Even if no one in the family has diabetes, you can still get it. Genes don't determine for sure, whether you'll get diabetes or not; they only influence the likelihood or the susceptibility to the disease. If both of your parents have the genes that increase the risk of diabetes, you'll be at a higher risk, even if your parents or family members do not actually have the disease.
In addition to genes you inherit, environmental factors play an important role, such as an unhealthy diet, or low levels of physical activity; this will increase your risk for obesity or type 2 diabetes. So, if family members eat a healthy diet and exercise, they may not have diabetes, but if you follow an unhealthy lifestyle, you might develop it.
For type 1 diabetes, the environmental risk factors are a little bit less certain, but there's some data that suggest that exposure to certain viruses or possibly even toxins in the environment that may contribute to the risk of the disease. So, if none of your family members have been exposed to the environmental risk factors, none of them will develop diabetes, but if you are exposed, you may develop diabetes.