Childhood diabetes isn't very common but there has been a threefold increase in the number of sufferers over the last 30 years. In Japan, 3 out of 100,000 children are affected with this chronic condition and in Europe and America, Type 2 Diabetics (the body does not produce enough insulin or the cells ignore the insulin) are growing in number partly because of the increasing trend towards obesity. However, obesity alone cannot be considered as the sole determinant in developing diabetes among children.
Some studies prove that heredity is one of the major causes of childhood diabetes. If both parents are suffering from Type 2 diabetes then their children will most likely have it as well. If both parents are under Type 1 diabetes though, there's only less than 20% chance that their children will suffer from the condition as well. What about identical twins? If one twin is a Type 2 diabetic, the chance for the other twin to suffer the same condition is almost 100% but for Type 1, there's only 40% to 50% chance that the second twin will develop the disease.
Heredity is not the only culprit though because there are some environmental factors that are also involved in the development of this chronic condition. Although there are ongoing clinical studies and research being conducted, the primary and specific cause of this disease is not yet fully understood and with this, it is safe to assume that diabetes can be caused by a combination of genes and environmental factors.