Most genetic responsibility for type ones lie with the father. Mothers can pass the trait on but it is less common. (3:1)The thing is that if it is the same father any future offspring of his has a much higher chance of developing type one diabetes than in the general population. The risk for another sibling being affected is 1:10-20
If you are very keen to have another baby there are a few other things to think about.
1. The baby still has a chance of not getting type one.
2. Life with type one is pretty bearable compared to many other things you could have (eg severe autism or Duchenne Muscular Dystrophy or cystic fibrosis)
3. With modern insulins, monitoring techniques and a restricted carb diet you can expect any baby to have a normal to near normal life expectancy even with diabetes.
4. There may be a cure during the baby's lifetime.
5. How would life be without a baby? Would you regret it?
6. What do Dad and your sons think?
Many kids would prefer a puppy over a sibling but even dogs and cats can get type one diabetes.